Transmitting circuitry for serial transmission of encoded information

ABSTRACT

The present invention provides reconstruction and resynchronization of wireless serial transmissions which are subject to fading causing erroneous uncorrectable bit errors exceeding the error correction code correction capacity present in frames of digitally encoded data. Valid data is reconstructed in frames which are determined to contain at least one erroneous uncorrectable bit exceeding the bit error correction capacity of the error correction code therein which have all erroneous uncorrectable bits within the error correction code bit held. A synchronization marker is transmitted with each frame group which does not represent any valid data in a frame. Detection of the synchronization marker by a digital signal processor after at least one frame is determined to contain at least one erroneous uncorrectable bit, which is indicative of a loss of synchronism of the receiving circuitry clock, resynchronizes the clock of a processor of the receiving circuitry. After resynchronization of the clock, frames beginning with the at least one frame containing the at least one erroneous uncorrectable bit indicative of the loss of clock synchronism to the frames in the frame group containing the synchronization marker are reconstructed to recover a data in frames which do not contain at least one erroneous uncorrectable bit and, as described above, to recover valid data bits in frames containing at least one erroneous uncorrectable bit. Finally, frames transmitted after the detected synchronization marker are processed synchronously including reconstruction or resynchronization as described above.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-In-Part of U.S. application Ser. No.08/112,256 now U.S. Pat. No. 5,446,759, filed Aug. 26, 1993, entitled"Information Transmission System and Method of Operation"; which is aContinuation-In-Part of U.S. application Ser. No.07/850,275, filed Mar.12, 1992, entitled "Low Power Information Transmission System HavingHigh Information Transmission and Low Error Rates and Method ofOperation" (now abandoned); Ser. No. 07/850,276, filed Mar. 12, 1992,entitled "High Speed, Low Power and Low Error Information Receiver andMethod of Operation" (now abandoned); and Ser. No. 07/850,487, filedMar. 12, 1992, entitled "Low Power Information Transmission andReceiving System Having High Information and Low Error Rates and Methodof Operation" (now abandoned), which applications are incorporatedherein by reference in their entirety.

Reference is also made to two related applications entitled "System forWireless Serial Transmission of Encoded Information" U.S. Ser. No.08/386,060 and "Receiving Circuitry for Receiving Serially TransmittedEncoded Information" U.S. Ser. No. 08/385,143, filed on even dateherewith, which applications are incorporated herein by reference intheir entirety.

TECHNICAL FIELD

The present invention relates to a method of one and two-way wirelessserial information transmission having a high rate of informationtransmission, a low error rate of transmission and transmission with lowradiated power, transmitting circuitry for encoding and transmitting theserial information, receiving circuitry for receiving and decoding theserial information, a receiver and transceiver using the receivingcircuitry, a transceiver using the transmitting circuitry, a signalprocessing system associated with a base station using the transmittingand receiving circuitry, and a system including the transmitting andreceiving circuitry having at least one receiver and at least onetransceiver and optionally at least one base station.

BACKGROUND ART

A. One-Way Wireless Transmission

There is a movement in the wireless industry towards providing more thansimple numeric telephone number messages. These messages are typicallyoriginated from personal and office computers and sent to the wirelesstransmitting system via the telephone network. These messages arereceived by the messaging system controller (paging terminal) andprocessed for transmission via the radio transmitting system.

E-mail services have gained tremendous popularity The average E-mailmessage is approximately 450 characters in length and 5 to 8 messagesare sent each working day.

Personal computers have become far more compact in size permitting themto "move" with the person verses remaining in a fixed location. It ispredicted that within the next few years, the majority of the personalcomputers will be less than 8 pounds in weight making them extremelyconvenient as a "portable office". This will make wirelesscommunications a media of choice to accommodate portable officecomputers to receive information services and E-mail messages.

This places an extreme burden on the existing radio infrastructure thatis allocated for messaging services. Currently, most metro area pagingsystems operating in the 150 and 450 MHz radio bands are operating at ornear full capacity accommodating current numeric paging subscribers.There is not adequate reserve air time available to accommodatealphanumeric information and E-mail services.

Nine hundred MHz authorizations are currently available for local andregional paging implementation. However, at the current protocol speedsand the projected growth rates, the national channels will undoubtedlyreach saturation within the next few years. Currently, one or more ofthe 900 MHz nationwide paging channels are close to such a saturation.There is a pressing need to increase the air time efficiency of theseradio paging systems. Furthermore, U.S. Pat. Nos. 4,849,750, 4,851,830,4,853,688, 4,857,915, 4,866,431, 4,868,562, 4,868,558, 4,868,860,4,870,410, 4,875,039, 4,876,538, 4,878,051, 4,881,073, 4,928,100,4,935,732, 4,978,944, 5,012,235, 5,039,984, 5,047,764, 5,045,850,5,052,049, 5,077,834 and 5,121,115 disclose a frequency agileinformation transmission network and frequency agile data receivers. Theabove-referenced patents are incorporated herein by reference in theirentirety.

U.S. patent application Ser. No. 702,939 now U.S. Pat. No. 5,436,960,filed May 20, 1991, entitled "Electronic Mail System with RFCommunications to Mobile Processors"; U.S. Ser. No. 702,319, filed May20, 1991, entitled "Electronic Mail System With RF Communications toMobile Processors Originating From Outside of the Electronic MailSystem" (now abandoned), U.S. Ser. No. 08/247,466 now U.S. Pat. No.5,438,611, filed May 23, 1994, entitled "Electronic Mail System With RFCommunications to Mobile Processors Originating From Outside of theElectronic Mail System and Method of Operation Thereof"; and U.S. Ser.No. 702,938 now U.S. Pat. No. 5,479,472, filed May 20, 1991, entitled"System for Interconnecting Electronic Mail Systems by RFCommunications," disclose a system for linking an electronic mail systemto portable computers using one-way wireless transmissions which may usethe network and receivers disclosed in the aforementioned patents. Theseapplications are incorporated by reference in their entirety herein.

Collectively, the above improvements utilizing the existing 150 and 450MHz radio messaging infrastructure will produce a significant reductionin the message delivery cost to the wireless subscriber. The cost todeliver a 450 character message with the system described in theabove-referenced patents has been projected to be approximately 65¢versus $1.50 for a 50 character message the industry is currentlyoffering subscribers. This significant cost reduction would furtherenhance the growth rate of the wireless information and E-mail serviceindustry.

Furthermore, allocated narrow band spectrum in the 220 MHz radiomessaging infrastructure is applicable to local and national datatransmission for applications such as electronic mail. However, thenarrow bandwidth of the channels in the 220 MHz. radio infrastructuredoes not support high data throughputs with prior art data protocols.

Adequate reserve radio spectrum is available in the 150 and 450 MHzradio bands in the form of IMTS mobile channels that have beenauthorized for one- and two-way information transmission to transmitdata and E-mail. However, a more reliable one-way messaging protocol isneeded to accommodate the need for information and E-mail services. Anadditional requirement for a more air time efficient (faster) messageprotocol exists.

The POCSAG protocol was originally authored by the British Post officecode Standardization Advisory Group. It was primarily developed for"tone only" or "semi-synchronous paging format". Unlike a synchronouspaging format that must be transmitted continually to maintainsynchronization of all the paging receivers, the POCSAG protocol issomewhat asynchronous in the respect that it only needs to send a radiosignal when messages are about to be delivered. However, a POCSAGprotocol transmission is extremely sensitive to atmospheric fades whichare discussed below. If a three bit error exists in a transmission ofinformation to a POCSAG protocol receiver, the BCH error correction codeembedded therein may be ineffective to prevent the transmissionsynchronism between the transmitter and receiver clock from being lostwhich results in a failure to complete the transmission of theinformation to the receiver and the receiver reverting into a scanningmode to attempt to lock onto a new transmission containing itsidentification code. A three bit error is produced by a fade inreception level below the detection level of the receiver for a timeinterval such as 2 to 4 milliseconds for 1200 and 512 baud data ratesrespectively.

To gain insight as to the POCSAG protocol, reference is made to FIG. 1for the following explanation. A POCSAG protocol frame set consists of aPREAMBLE, a SYNC signal, and eight frames that are subdivided into twocode words each. POCSAG protocol pagers are synchronous in the respectthat once they detect the PREAMBLE and synchronize on the SYNC codeword, they only then search for a message in their respective frame. Ifcapcode ID numbers are consecutively assigned, the page is automaticallyassigned to a respective frame. Taking the binary equivalent of the lastthree digits of the ID of the pager, it is possible to determine inwhich one of the eight frames a respective pager would be located.

The POCSAG protocol pager is continually sampling the radio channel tolook for its PREAMBLE. The PREAMBLE is typically 1.125 to 3 seconds induration, and consists of an alternating string of ones and zeros sentdigitally. When the pager samples the radio channel and determines thePREAMBLE string, it remains on and searches for the SYNC signal. TheSYNC signal is actually a 62.5 millisecond code word that transmits afictitious address to which the pagers respond. It is an unused address,and therefore does not cause falsing (erroneous turn on) of otherpagers. Upon receiving the SYNC code word, the pager searches for amessage in its respective frame group.

The POCSAG protocol has some inherent inefficiencies in its design.These inefficiencies exist in both 512 and 1200 baud POCSAG protocolpagers and are inherent in the architecture of the POCSAG protocol. Inthe POCSAG and other digital protocols, the baud rate is also thefrequency of the subcarrier (e.g. 512 baud uses a 512 Hz. squarewavesubcarrier which is modulated with ones and zeros to encode the parts ofa transmission). Referring again to FIG. 1, it should be noted that aframe consists of code word one and code word two. If a POCSAG protocolpager receives a message, the first code word of its frame contains theID or address information for the pager. It also contains alertinginformation to indicate to the pager what types of beeps are beingissued. Code word two contains the numeric or alphanumeric information.When the pager is in numeric mode, the code word can contain fivenumeric digits.

However, it should be noted that very few numeric pages are five digitsin duration. In fact, in a typical paging system, 98% of the numericmessages are seven digits in duration as illustrated in FIG. 2. Becausethe numeric message is seven digits in duration, the POCSAG protocolpermits a borrowing or an extension into the next frame. The first codeword in each frame (which would typically be an address), has a markerbit that indicates whether the code word contains address or numericinformation. The remaining two digits of the seven digit example thenspill over into the first code word of the next frame. Of the twentybits of data (five numeric digits) in the next frame word, only eightwould be used rendering the balance of the code word useless. The POCSAGprotocol fills the balance of the code word with "filler code". Thesecond code word of the adjacent frame is also back filled with fillercode. The adjacent frame is unavailable for use by any other page. Infact, any message awaiting an adjacent frame two pager, must wait untilthe next frame group is sent in order to receive the message. Thearchitecture of a POCSAG protocol based system requires that a messageto a given pager be sent only in its respective frame.

It is obvious that unless great care is utilized in the distribution ofreceivers to divide the receivers evenly within the frame groups, andthat the customer usage in each frame group is equal, severe system airtime inefficiencies are obtained. System air time efficiencies can varybetween 30 and 60%. A great deal of the air time cannot be fullyutilized as it is due to the message length (seven digits) and is causedby the insertion of filler codes. If a per message comparison of pagingprotocols is made, it does not take into account the inherent systeminefficiencies when numerous pages are sent. As mentioned previously,POCSAG protocol efficiencies vary considerably if a great deal ofattention is not paid to the proper distribution of ID codes.

To gain some insight as to how the POCSAG protocol tends to reduce theair time efficiency, reference is made to FIG. 3. FIG. 3 shows fiftynumeric pages that need to be sent via the paging system. For purposesof this example each page is a seven digit numeric page and the pagersare equally distributed between the eight frame groups.

The first problem is that due to each page being seven digits induration, only an average of 3.5 pages can be sent per frame group. Itshould also be noted that a seven digit numeric page destined for theeighth frame group necessitates that a SYNC signal be sent. The messagethen spills over to the first frame of the next frame set. An "overhead"problem that also becomes obvious is that the receivers must beresynchronized after the transmission of the first eight frames. Thisresynchronization adds to the length of each message sent within theeight frame group. SYNC is 62.5 MS divided by 31/2 pages to apportionoverhead. One hundred sixty seven milliseconds of the 267 MS periodproduces a 62.5% efficiency. Due to the spilling over of messages intotheir adjacent frames, it is seen that a second problem is precipitated.Assuming that each of the pages arrive in frame group order (e.g.1234567, 1234567), it is seen that even if the paging terminal can sortto get the maximum 3.5 message per frame group efficiency, that a numberof pages destined for the first frame tend to build or stack up. Toeliminate this problem, fewer pagers may be issued in the eighth framegroup (which spill over into the first frame group). However, theproblem is not solved by doing so, and simply a build up of other pagesin other frame groups occurs.

The 512 baud POCSAG protocol transmits 2.857 alphanumeric characters per62.5 MS code word. If an alphanumeric message is transmitted in thefirst frame, a maximum of forty two characters can be sent before a 62.5SYNC signal is required.

    ______________________________________                                                       Maximum Characters                                             Transmitted Frame                                                                            Before Sync                                                    ______________________________________                                        1              42.8                                                           2              37.14                                                          3              31.43                                                          4              25.71                                                          5              19.99                                                          6              14.89                                                          7              8.57                                                           8              2.85                                                           ______________________________________                                    

As the national average length of an alphanumeric message is forty fivecharacters, it is reasonable to add the SYNC overhead to the charactertime. The average E-mail message is considered to be from 150 to 450characters, which increases the air-time requirements and increases theprobability for a reception error.

Each character would be:

    ______________________________________                                        21.98 m.s.      Per character                                                  2.73 m.s.      Frame OVHD per character                                      24.71 m.s.                                                                    ______________________________________                                    

Current digital protocols (POCSAG and Golay) are difficult to speed updue to their respective architectures. Attempts to increase POCSAGprotocol speed from 512 to 1200 or 2400 baud (subcarrier frequency) haveencountered the following problems.

The 1200 and 2400 baud data transmission rates have shortened the databit time to approximately 800 and 400 microseconds respectively. Thisshort time per bit produces a marked degradation in message receiptreliability for lengthy alphanumeric messages.

POCSAG protocol receivers have a BCH error correction scheme that cantolerate only one or two bits per frame to be erroneous before thetransmitted character is unrecoverable. Man-made noise and Rayleighfading phenomenon are very prevalent for such short bit times. The netresult is that the cumulative effect of the error correction scheme thatthe current digital protocols utilize in combination with the effects ofnatural and man-made interferences degrade the message receiver'sreliability when attempts are made to accommodate information and E-mailservices. A three or more bit error represents a fade below thethreshold detection level of the receiver which can cause the receiverclock to loose synchronism with the transmitted information, turn offand search for another transmission of its address. A three bit errorrepresents a true message error which results in the loss of at leastsome data.

Speed per message is actually a relatively poor method to choose whichformat (type) of pager to utilize on a system. There are subtledifferences in the various alpha signaling schemes that have far moreimpact on the reliability of the paging system and its ability todeliver message information to pagers. Differences in air timeefficiencies and the techniques employed to correct erroneously receiveddata by the pager are very important considerations that should be made.

The POCSAG and Golay protocols have digital formats requiring digitaltransmitters.

The 512 baud POCSAG protocol utilizes thirty one bit words, utilizingeleven of the bits for error correction. A three bit error in theaddress, as stated above, causes the message to be missed. This equatesto a four millisecond fade or noise burst during the address and a twomillisecond fade error during the message. Twelve hundred baud POCSAGprotocol pagers have the same error correction format and air timeinefficiencies. The fade resistance is reduced to a two millisecond fadeduring the address and one millisecond during the message. Although thenumber of pagers on a given channel is doubled, the degradation ofmessage reliability due to the reduced fade resistance becomesnoticeable with numeric paging, and markedly poor when long alphanumericmessages are sent.

The Golay protocol utilizes twenty three bit words, utilizing eleven ofthe bits for error correction. The Golay protocol transmits the ID codeat 300 baud to increase the decoding reliability. The message istransmitted at 600 baud. The Golay protocol has an increased reliabilityfor detecting the ID portion of the page due to the slower data rate.However, the overall signalling when the format is analyzed isnoticeably slower than 512 baud POCSAG protocol, making it a poor choiceto attempt to accommodate alphanumeric information and E-mail serviceson a radio channel that is currently accommodating tens of thousands ofnumeric pagers.

In the late 1980's A European consortium of countries formed a committeeto develop a Pan-European wide paging network that would meet therequirements for the European traveling paging marketplace.Representatives from each country participated in a committee-likefashion to develop a new paging protocol that would allow the equivalentof an international paging network with common frequencies and a commonprotocol, permitting all countries to effectively offer Pan-Europeanpaging services. The European Radio Message Service (ERMES) committeewas formed and developed both a new multi-level FSK paging format andall of the corresponding network architecture to relay messages to thetransmitting infrastructure in Europe.

A multi-level FSK modulation technique is used with the ERMES protocolthat modulates the transmitter at 3200 baud with each baud or FSK levelrepresenting two bits of binary information. The effective data rate ofthe ERMES protocol is therefore 6400 bits per second. The multiple baudlevel FSK modulation technique suffers from a reduced signal to noiseratio of six dB consequent from the lower level of the two levelmodulation being closer to the noise level of discrimination of thereceiving circuits. Loss of signal level for a substantial time belowthe noise level results in loss of synchronism which terminatesreception of the remainder of the message resulting in a catastrophicmessage reception failure.

With a number of years of experience in utilizing the POCSAG protocol,the ERMES committee corrected some of the inherent deficiencies of thePOCSAG protocol. By the same token, many parts of the architecture ofthe POCSAG protocol were utilized in the adoption of the ERMES protocol.

Somewhat later than the development of the ERMES protocol, a movementoccurred in the United States to develop a more reliable radio messagingprotocol. Although there are some manufacturers that have attempted togive proprietary names to this American protocol, it has typically beencalled the modified ERMES protocol. This is in part due to the fact thata large percentage of this modified ERMES protocol derived itsarchitecture from the ERMES standards. Unlike the ERMES protocol, whichis exclusively synchronous and transmits only at 3200 baud, the modifiedERMES protocol has been proposed in three distinct phases. This is inpart due to the fact that the American marketplace did not have a newband of frequencies allocated exclusively for national paging use. Themodified ERMES protocol has to have the flexibility in its design topermit co-residing on currently operating radio messaging channels thatcontain POCSAG and Golay protocol pagers.

Phase one of the modified American ERMES protocol will utilize a 1600baud FSK architecture that permits it to be compatible on existingdigital base stations with other digital paging formats. Phase two,although not currently well defined, will transmit at 3200 baud with a3200 bit per second rate utilizing multiple level FSK transmission.Phase three will utilize 3200 baud multi-level FSK modulation with eachFSK level representing two bits of information for a 6400 bit.transmission rate.

The 1600 baud modified ERMES protocol has been designed as atime-slotted, fully synchronous protocol. It derives much of itsarchitecture from three previous signaling technologies. Messageinterleaving to increase fade resistance and the basic structure of theerror correction and data blocks are derived directly from the EuropeanERMES protocol. The time synchronization techniques are similar toprevious RDS and MBS synchronous subcarrier systems that were developedin Europe for subcarrier messaging. The basic BCH error correction codeand messaging architecture have been derived from the POCSAG protocol.

The 1600 baud modified ERMES protocol consists of 128 frames ofinformation that are sent over a period of four minutes. A frame iscomposed of 150 MS of synchronization preamble and eleven blockscontaining information each being 160 MS in duration.

The 150 MS of synchronization preamble contains three basic componentscalled sync one, frame information, and sync two. The sync one portionpermits the receiver to synchronize upon waking up during its respectiveframe. Frame information is then transmitted that can alert the receiveras to the proposed data rate that would be transmitted during thebalance of the frame.

Sync two then permits the receiver to transition to the new baud rate ifindeed the baud rate is different than 1600 baud.

The eleven blocks of information that follow the synchronization aretypically divided into three categories. Blocks zero and one aretypically utilized for addressing of the receivers contained within thatframe. Approximately eight addresses can be contained per blockpermitting as many as sixteen receivers to be addressed in a singleframe. Block two typically contains message vectors. A message vectorpoints the receiver that was addressed in block zero or one to afollowing block to locate its messages. Blocks three thru ten will thencontain messaging information for the receivers addressed in blocks zeroand one.

The eleven blocks of information that follow the synchronization aretypically divided into three categories. Blocks zero and one aretypically utilized for addressing of the receivers contained within thatframe. Approximately eight addresses can be contained per blockpermitting as many as sixteen receivers to be addressed in a singleframe. Block two typically contains message vectors. A message vectorpoints the receiver that was addressed in block zero or one to afollowing block to locate its messages. Blocks three thru ten containmessaging information for the receivers addressed in blocks zero andone.

Like in the POCSAG protocol that has been previously described, a BCHerror correction code is utilized with the modified ERMES protocol withthirty-two bits per frame with eleven bits of error correction code topermit the receivers to correct bit errors up to a two bit error.Furthermore, the messages are interleaved so that all of the bits for aparticular numeric or alphanumeric character are not transmittedsequentially. The low order bits of each character are transmittedfirst, followed by ascending order binary bits until the entire messagehas been sent. This increases the fade resistance of the 1600 baudprotocol to approximately ten MS. Each block contains eight thirty-twobit words that then permit each word to contain five numeric digits or2.85 seven bit alphanumeric characters. This portion of the 1600 baudprotocol is identical to that of the POCSAG protocol and itsarchitecture. Each block is therefore capable of containing as many asforty numeric digits of 22.8 seven bit alphanumeric characters.

Like the POCSAG protocol, certain restrictions apply to the 1600 baudmodified ERMES protocol. Any portions of a block that are unused bymessage information must be filled with filler code. This introduces thesame type of inefficiencies that are present in the POCSAG protocol.

As the eight words within a block have to contain five numeric digitsand the bulk of numeric messaging requires seven digits, a significantpercentage of filler code must be utilized to fill in the remainder ofthe unused words within a block.

A second inefficiency exists in the inherent architecture of the 1600baud modified ERMES protocol that also exists in the POCSAG protocol.Pagers are selectively assigned to "time slots" and can only receivemessages during their respective time slot, therefore great care in theeven distribution of time slots (pager ID's) must be exercised. Like thePOCSAG protocol, the 1600 baud modified ERMES protocol relies on therandomness of paging events to prevent excessive time delays beingcaused by multiple messages to pagers within the same time slotoccurring at the same time. However, the 1600 baud modified ERMESprotocol has a further encumbrance that its overall cycle time can be aslong as four minutes. If the receiver's frame is unavailable due to highmessage traffic, it could wait as long as four, eight, or twelve minutesto receive its message.

This differs considerably from the POCSAG protocol in terms of timelatency as POCSAG goes through a complete cycle in slightly over 1second. If a POCSAG protocol frame for a respective pager is filled withother messages, the next frame will be available for transmission in onesecond.

To overcome this problem, the 1600 baud modified ERMES protocol hasproposed utilization of less than the full one hundred twenty eightframes. However, this tends to have two factors that are detrimental tothe paging subscriber. The first is a respective shortening of batterylifespan, and the second is a crowding of receivers into theirrespective frames. This crowding and clustering of receivers intosmaller numbers of frames will tend to extend the waiting period bymultiples of time that are dependent upon how quickly the frames cycle.

It has been proposed that in order to allow the 1600 baud modified ERMESprotocol to be intermixed with current POCSAG protocol traffic, theframe duration should be shortened to one cluster of frames per minute.This basically introduces a sixty second time delay that, when averaged,would equal at least a thirty second message latency. However, duringpeak busy hour periods, this latency would be in multiples of not thirtyseconds average, but thirty seconds for the first delay plus sixtyseconds for each delay cycle thereafter. Simply explained this meansthat if a pager were to have to wait until the next frame, there wouldbe an average delay of thirty seconds plus sixty seconds, or ninetyseconds total. If the delay were to be two frames, it would be thirtyseconds average plus sixty seconds average plus sixty seconds or two andone-half minutes.

Like the POCSAG protocol, the air-time latencies degrade the modifiedERMES protocol considerably when addressing alphanumeric messaging. Thenational average for an alphanumeric message is forty characters. The1600 baud modified ERMES protocol (like POCSAG) can borrow blocks ofinformation to permit the forty character message to be delivered to areceiver. As each block has a maximum capacity of 22.8 characters, twoblocks will be needed to transmit the alphanumeric message. If messagesof longer duration are desired, the maximum character length for asingle frame would be approximately one hundred eighty characters.

Like the POCSAG protocol, the 1600 baud modified ERMES protocol utilizesonly seven bit characters. In order to address eight bit characters (ascommonly used by computers), it is necessary to send commands thatpermit the receiver or external device connected to a receiver to permitthe equivalent of straight binary information to be transmitted. Thisplaces a great deal of overhead on the external devices to receive thisbinary information and process it into true eight bit characters afterdecoding the interleaving and BCH error correction codes.

In terms of protocol efficiency, it appears that the 1600 baud modifiedERMES protocol has slightly more overhead than the POCSAG protocol.Although the address information is similar to the POCSAG protocol,additional information containing message vectors must also betransmitted to the 1600 baud receiver. As the block architecture and theBCH error correction code are identical, this would tend to lower theeffective data throughput rate of the 1600 baud modified ERMES protocol.

A potential for interference exists when POCSAG and modified ERMESprotocol pagers are interleaved on a channel. The POCSAG protocoltypically transmits at 512 baud. The time per baud is 1953 microseconds.The 1600 baud modified ERMES protocol has a time duration of 625microseconds per baud. Three bauds would equal 1875 microseconds. Acomparison of the 1875 microsecond baud duration and the POCSAG protocol1953 microsecond duration, yields less than a 5% time differential.

POCSAG protocol pagers, in order to quickly synchronize to the preamble,have a relatively wide synchronization bandwidth. For example, a 512baud POCSAG protocol pager is capable of synchronizing to any data ratebetween 400 and 600 baud. This wide bandwidth is necessary to allow thePOCSAG protocol pager to synchronize in a minimal amount of time to thePOCSAG preamble. Although somewhat of a misnomer, the preamble isactually the portion of the POCSAG protocol signal that timesynchronizes the receiver. The sync word that follows the preamble onlyserves to tell the pagers the correct bit timing order. The sync word isactually an unused ID or capcode that the POCSAG protocol pager searchesfor to obtain a match. Once a match is found, the POCSAG protocol pagercan then establish the bit order or significance and can then beginproper decoding of the binary information that follows. It also uses thesync word to begin counting to permit it to decode a message in itscorresponding frame.

As a POCSAG protocol pager detects the 1600 baud data rate transitions,it attempts to search for the synchronization or the sync code word.During the presence of 1600 baud information, the POCSAG protocol pagerremains on for as long as several seconds after the completion of 1600baud data transmission. As will be described later, this causes a severedegradation in the POCSAG protocol receiver's battery life when attemptsat intermixing 512 and 1200 baud POCSAG protocol receivers with the 1600baud modified ERMES protocol are made.

The 1600 baud data transmission of the modified ERMES protocolapparently has another adverse effect on the POCSAG protocol receiver.As a consequence of POCSAG protocol receivers relying on the preamble todetermine their bit timing synchronization and having to maintain suchsynchronization for at least one second, another detrimental effect inthe intermixing of the 1600 baud modified ERMES protocol with the POCSAGprotocol is experienced. Once POCSAG protocol receivers synchronize tothe 1600 bit per second data rate, they are not capable of re-syncing tothe true POCSAG data rate if a POCSAG message immediately follows a 1600baud message. To overcome this problem, one manufacturer has recommendedthat a POCSAG protocol warm-up be transmitted after a 1600 baud modifiedERMES protocol message has terminated. This "POCSAG protocol warm-up"consists of 400 MS of 750 baud data of zeros and ones to be transmittedprior to the transmission of a 512 baud POCSAG protocol message.Although it has been termed a POCSAG protocol warm-up, it is quite tothe contrary. Sending 750 baud to a POCSAG protocol pager will not causethe POCSAG protocol receiver to wake-up and attempt to synchronize.However, if the POCSAG protocol pager were on and synchronized to the1600 baud modified ERMES protocol, the transmission of the POCSAGprotocol warm-up will immediately cause the POCSAG protocol pager toreturn to sample mode. Therefore, it appears that this 750 baud POCSAGprotocol warm-up is instead a de-sync signal.

A common misconception in the wireless industry concerns the term "baudrate". It is easy to conceive that a higher baud rate directly controlsthe number of pagers per channel. This is in part due to the fact thatbaud rate as pertaining to computers is thought in "wireless" terms whena calculation as to the character speed is determined. Typically, acomputer sends eight to eleven bits of information per character, andone simply divides that number into the baud rate to determine how fastinformation is transmitted. The fact is the baud rate is only a portionof the analysis. Unlike wireline computers that are connected withtelephone lines, radio transmission requires additional "overhead" to beadded to the signaling protocol due to its "one way" nature. Radiopaging or one-way information transmission does not have the wire-lineor two-way wireless privilege of requesting a second transmitted messageif an error is received. Radio paging is a "one time" transmission thatis "one way". Manufacturers of radio paging equipment therefore mustencode additional information to permit the pager to correct errorscaused by radio transmission problems. Instead of eight to eleven "bits"representing a character, as many as thirty bits may be required. Thiscorrection overhead is called "error correction", and in some methodsreduces the data transmission rate to the pager by as much as 75%. Ifhalf of the 1200 baud data rate is utilized for error correction, theeffective data rate is 600 baud. The speed or "baud" rate is furtherreduced by "overhead" SYNC and "wake-up" preambles that must be sent toprepare the paging receiver prior to the transmission of an actualmessage.

Error correction code embedded in a frame of data bits is used toserially process the bits of the frame to correct minor bit errors suchas one or two bits which occur anywhere in the frame. The serialprocessing of the bits of a frame which contain data and errorcorrection code is typically implemented with a series of EXCLUSIVE ORgates. When a number of bit errors in a frame exceeds the errorcorrection capacity of the error correction code, the data within theframe is erroneous. The prior art methods of wireless data transmissiondo not permit the recovery of valid data bits from a frame containing anumber of bit errors which exceed the bit error correction capacity ofthe embedded error code which for most types of data transmissionprotocols is two bits.

The operating environment has by far the greatest impact on thereliability of the paging system. Geographical terrain, the operatingfrequency, the presence of man-made structures, and natural and man-madenoise all have a collective impact on the operating efficiency of thecurrent state of art in paging systems. If the radio signal cannot reachthe paging receiver, the sensitivity of the receiver or the errorcorrection in the protocol has little purpose. The first requirement ofa paging system is to therefore provide a good radio paging signal atall the areas of the paging system's service area.

Geographical terrain of the paging service area determines the number oftransmitter sites and the antenna patterns required to provide thenecessary "Carey" coverage or service area. The less the variation interrain, the more evenly distributed the RF field is, and the easier itis to obtain reliable service area coverage. Man-made objects (such asbuildings) and geographic variations (hills) tend to cause shadows byblocking the "line of sight" paging signal. In a metropolitan radioenvironment, the receiver is subjected to a very hostile environment.The paging receiver is subject to multi-path interference, impulsenoise, simulcast beats, and in many systems with multiple transmitters,non-synchronization of the transmitters. These phenomena are furthercompounded by building shadow effects and building penetrationattenuation of the signal. All of the mentioned phenomena serve toreduce the reliability of the receiver. Higher power transmitters andmultiple transmitters can alleviate a portion of the aforementionedproblems, and increase other problems (e.g. multi-path, simulcast beats,and non-synchronized transmitters). It is not a simple problem toresolve, as numerous other problems exist which complicate thereliability of radio messaging services in a given area.

Previously, analog pagers utilized forms of active filters to decode theaddressing tones. The active filters in the pagers were very sensitiveto any form of phase or any other form of distortion that modified thesinusoidal signaling wave forms. Analog pagers required a "perfect" sinewave to properly decode and alert the user. Hence the reason for precisephasing of transmitters and synchronized transmitters (simulcast)systems were necessary to accommodate the active filter decoders in thepagers. Even with synchronization and, proper phasing of the station,the pager often decoded unreliably when located at the midpoint betweentwo transmitters.

The move to digital encoding methods resulted from these former analogproblems. In the early 1980's, digital transmitting and paging productswere introduced by manufacturers that did not experience the problemsassociated with analog pagers. It was thought of as the only method toreliably send numeric data to a paging receiver. Considering that in1980 analog technology was limited to 300 baud and yet digitaltechnologies could transmit 600 to 1200 baud data, this was correct. Itwas not an inexpensive move, as literally every piece of equipment inthe carrier's system required replacement. Paging terminals, basestations, and modems had to be purchased to replace the existing analogequipment. Digital paging also required that additional base stations beadded to provide the increased signal strength necessary for reliabledata stream reception by the pager. The deficiencies found in the analogtechnologies were eliminated by the move. Digital pagers did not sharethe problematic phase errors found in their analog counterparts.Research for new developments in analog technologies were abandoned bythe pager manufacturers for several reasons. Analog technology was notas advanced in the early eighties (digital signal processing of analogsignals was not available), and by emphasizing sales of digital systems,communication equipment manufacturers could increase sales ofreplacement base stations and paging terminals dramatically.

In this decade, advances in analog decoding technology have increaseddramatically. Data transmission rates of 19,000 baud on ordinarytelephone lines are common (as compared to 300 baud in 1980).Microprocessor assisted digital signal processors are available on asingle chip with decoding sensitivities unheard of in 1980.

Even with the increased transmitter maintenance, the cumulative effectsof mis-synchronization of the radio transmitters, Rayleigh fading, andman-made noise reduce the reliability of the current digital receiversnoticeably. The overall fade tolerance at 2400 baud is less than onemillisecond. A gap in the data transmission in excess of one millisecondcauses the message receiver to terminate the receiving process.

There is a need in the art for a messaging protocol to be compatible onboth analog and digital radio transmitting systems. The above-referencedpatents disclose a protocol which is compatible with analog and digitaltransmitters. The protocol disclosed in these patents is approximately99% reliable for the transmission of a 450 character message but isslower than the POCSAG protocol by a factor of approximately four. Theprotocol disclosed in the above-referenced patents like the POCSAG andGOLAY protocols transmits serial data frames with embedded errorcorrection code. This protocol is immune to a fade duration of up to 100milliseconds. The radiated power required to broadcast this protocol isapproximately equal to that required for the POCSAG or Golay protocols.

The majority of the messaging radio transmitting systems (220 MHz. hasless) have radio channels allocated that utilize 5 KHz transmitterdeviation limits and transmitted audio bandwidths that are limited to300 to 3000 Hz. The digital transmitters currently in service havemodems that may limit the data rate to 1200 baud (1200 Hz. subcarrier).Compatibility with the current transmitter infrastructure with any newprotocol is imperative to provide universal compatibility. The 1200 baudlimitation is typically a constraint by the current design of theintegrated modems which the digital base stations utilize. The bandwidthof current radio transmitters can accept faster data rates if thebandwidth of the digital modems is increased.

As is apparent from the description of the POCSAG protocol above, theseare fundamental problems of increasing its data throughput. The problemsare caused by the propensity of atmospheric serial informationtransmission to semi-synchronous receivers to be subject tounpredictable interruptions caused by atmospheric fades which degradethe atmospheric transmission below the noise threshold of the receiver.As has been pointed out above, a three bit error may cause a total lossof synchronism between an information transmission and a POCSAG protocolreceiver from which the receiver cannot recover with the remainder ofthe transmission after the fade being lost with the receiver going intoa search mode to look for another transmission of an address of thereceiver.

When the probability of a loss of synchronism becomes high, the use of atransmission medium goes down. The POCSAG protocol has a reliability ofaround 95% for a seven character message which means that a 5% chanceexists of losing one or more digits of the transmission. A higherreliability is needed for data transmissions between computers to makeone-way serial atmospheric data transmission a widespread methodology.

An analysis of atmospheric transmission using the prior art protocols inaccordance with accepted mathematical relationships for evaluatingatmospheric radio frequency transmissions follows which reveals thatthey are poorly suited to data transmissions of more than a fewcharacters in length. ##EQU1##

The threshold ST is the receiver threshold detection level and themedian SM is the median field strength level. ##EQU2##

The quantity t is the net probability of a fade divided by the mean rateof fading and equals

    1/2rF.sub.o (e.sup.+0.693r.spsp.2 -1)                      (5)

The fading rate F_(o) is the natural frequency at which atmosphericradio frequency transmissions periodically fade as a function of thechannel frequency F_(o) and the speed of the receiver or transceiver ifthe system is a one-way or two-way wireless system in miles per hour;the fade length t in seconds is the length of fade; the fade belowthreshold F_(R) is the time duration in seconds that a transmissiondrops below the detection capability of the receiver; and theprobability of message loss P.sub.(error) is the probability that amessage transmission will not be completed as a result of a lost ofsynchronism between the data transmission and the receiver. See S. O.Rice; Statistical Properties of a Sine Wave Plus Random Noise; BellSystem Technical Journal, January, 1948; T. A. Freeburg; An AccurateSimulation of Multipath Fading; Paper;1980; Caples, Massad, Minor; UHFChannel Simulator for Digital Mobile Radio; IEEE VT-29; May 1980; and P.Mabey, D. Ball; Application of CCIR Radio Paging Code No. 1; 35th IEEEV.T. Conf.; May 1985 for a discussion of the above-referenced equations.

FIG. 4 illustrates a diagram of a prior art encoding mechanism used toencode prior art paging protocols such as POCSAG, GOLAY, 2 Tone and 5/6Tone, etc. This encoding mechanism has also been used to encode anddecode two-way mobile data formats. This encoding mechanism is a Hi-CapMultiswitch Model DMF-4000 manufactured by ESA Telecom Systems Group,Inc. of 10345 S. Oxford, Chicago Ridge, Ill. 60415. The encodingcontains the necessary microelectronics to encode the protocols andforward them to the transmitter. The encoding mechanism utilizes adistributed processing architecture to permit the receipt of messagesfrom the public switch telephone network (PSTN), provides the necessarysubscriber verification and validation, encodes the protocols, and gainaccess to the radio transmitting system. The higher level processorconsists of a central processing unit 30, a read only memory 32 thatcontains the BIOS, a random access memory 34 that stores in buffers bothmessage and system operational information, a hard and soft disk drive36 that are utilized to store the main operating program and subscriberfile information, a printer/billing port 38 for the logging of systemactivity and service updates, maintenance port modem 40 for diagnosticsin the event of a system malfunction, and a resident keyboard andmonitor 42 to allow access to the main processing unit for addition ofsubscribers and system maintenance.

The main processor, which is comprised of items 30-42, contains thesystem operating program and control mechanisms that communicate to theperipheral modules 46-56 via the PCM matrix switch and data boardbuffers 44 and bus 58. The PCM matrix switch 44 contains the digital andaudio matrix that permits any of the resident modules 46-50 to sendaudio and digital information between each other and the main CPU. It isalso responsible for buffering data from and to the various peripheralmodules 46-56 to permit the system to grow in size to accommodate themessaging traffic as needed. Each of the peripheral cards 46-56 containsone or more board resident processors that further process informationand relieve processing overhead from the main CPU. It is with thisdistributed processing architecture which permits the encoding mechanismto be expanded to accommodate several hundred input ports and numerousradio channels. When the encoding mechanism is connected to a two-waysystem, dotted line bidirectional arrows are used to identify thetwo-way communication paths. Additionally, the radio station control maybe comprised of multiple modules which each are connected to one or morebase stations (not illustrated).

In order to gain a complete understanding of how the encoding mechanismof FIG. 4 functions, it is advantageous to understand how a message isprocessed from receipt by the encoding mechanism from the PSTN andultimately delivered to the radio transmitting system connected to theencoding mechanism for transmission to the receiver. To send a messageto the receiver, a message originator calls via the public switchtelephone network PSTN to one of the encoding mechanisms telephoneports. Three telephone port configurations are described here beingdirect inward dial trunks 46, direct outward dial trunks 48, and/ormixed frequency trunks 50 which can both answer and originate calls. Thethree basic trunk configurations are necessary to accommodate thevarious telephone interfacing requirements that are necessary tointerface from the PSTN to the encoding mechanism at its particularlocation. Details of the trunk configurations are known. The modemsfunction to convert digital formatted information to analog fortransmission by telephone lines. The protocol encoder 54 permitsmultiple protocols to be encoded which is common with paging systemswhich sequentially broadcast in different protocols. The radio stationcontrol interfaces the encoding mechanism with a radio transmitter orradio system control. If the protocol encoder 54 is encoding two-wayprotocols, one or more radio station controls 56 and/or one or morebidirectional lines are connected to the one or more radio stationcontrols.

Upon receipt of the message recipient's telephone or ID number, themessage entry process begins. The main CPU 30 looks up in the customerfile the necessary message decoders that must be connected to thepreviously described telephone trunk modules. Referring to FIG. 4, themain CPU 30 may connect any number of modems individually orsimultaneously to permit the decoding of medium to high speed serialdata decoders. This is accomplished by connections through the PCMmatrix switch 44 to one or more modem modules 52 that are connected tothe digital data and PCM bus highways 58. In some cases it may not beknown which type of entry modem or entry protocol is being used, and inthis situation the resident decoders on the respective telephone trunkmodules 46-50 are responsible for decoding DTMF entry protocols andhigher speed modem protocols are decoded by the modem modules 52.

The encoding mechanism of FIG. 4 is designed to receive numerous numericand alphanumeric entry formats from the message originator. They includeDTMF (Dual Tone Multiple Frequency) overdial for a numeric message thatcan be directly encoded from a telephone keypad. An alphanumeric DTMFentry process can be entered by a two button press entry scenario thatcorresponds to the desired alphanumeric character that is displayed onthe keypad. Message originators that are utilizing a PC that have amodem can also enter a similar DTMF alphanumeric format by softwarepackages that reside in the PC that direct the PC's modem to send DTMFtones. All of the aforementioned DTMF message entry formats are decodedby resident DTMF decoders on the respective telephone trunk modules.

Higher speed formats utilizing Bell and CCITT formats permit messages tobe sent at 300, 600, 1200 and 2400 baud formats. In the event that thehigher speed protocols are utilized, a modem module 52 is connected tothe respective telephone trunk module via the digital data and PCM databus 58. The modem module 52 is capable of auto-adjusting to the desiredspeed and format of the message originators modem.

Upon completion of receipt of the message, the main processor 30 isalerted to permit a message transfer. In the event of a DTMF message,the message has been temporarily stored on the respective telephonetrunk module, or in the event of a higher speed data message it isstored and temporarily buffered on the modem module 52. The message isthen transferred to the main CPU 30 for further processing via the databus buffer module 44. The main CPU 30 then looks up in the customer filethe format of the receiver and stores the message in the respectivebatch buffers for that particular encoding format. The encodingmechanism described is capable of encoding numerous signalling formatsthat include analog 2-tone,5/6 tone, POCSAG and Golay protocols.

In order to optimize and obtain the maximum air-time efficiency,messages for receivers with like signalling protocols are buffered andbatched and are controlled by two entries that are programmable via thesystems menu. The two entries are time and volume related. The number ofcharacters that can be transmitted when the system controller gainsaccess to the radio transmitting system are programmable as well as apredetermined period of time and/or both. In the event of very lowtraffic periods, it is typically the time entry that will precipitatethe transmission of the messages that are stored in the main processor'sbatching buffers. In the event of high activity, it is the volume ornumber of characters that trigger the main CPU 30 to initiate accessingthe radio transmitting system.

B. Two-Way Wireless Transmission

1. PCS, PCM and Mobile Data Services

There is a movement in the wireless industry towards providingsophisticated two-way data services to address the rapidly growing datamarketplace. The Federal Communications Commission has auctioned newfrequencies for new data services in frequency bands of 900 MHz. andabove. There is also an ongoing re-evaluation of the existing radioservice providers to evaluate their currently allocated radio spectrumto determine if they in turn can also address this new data marketplace.

Cellular system operators have evaluated their existing cellular mobiletelephone frequencies and have determined with a minimal amount ofhardware modification, data services can be directly addressed by theircurrently allocated and operational cellular channels. These frequenciesreside in the eight hundred megahertz radio bands.

SMR system operators are also evaluating the utilization of theircurrently licensed frequencies. Historically utilized for voicedispatch, they are currently modifying their equipment architectures toaccommodate the transmission of data. The SMR carriers are alsoattempting to adopt common data protocols that will permit the formationof wide area data systems that are compatible from region to region andfrom state to state.

Dormant IMTS mobile channels are also being evaluated (these exist inboth the one hundred fifty and four hundred fifty megahertz radio bands)that also could accommodate mobile data services to address themarketplace.

To summarize, there are numerous frequencies that are available in theone fifty, four fifty, eight hundred and nine hundred megahertz radiobands that are currently allocated for two-way services that couldinclude the transmission of data services based upon serial dataprotocols. Both one-way and two-way wireless systems use serial dataprotocols which have the common property that a single subcarrier ismodulated to encode a single stream of serial information. A portion offrequencies to be auctioned by the Federal Communications Commission areto be for data services.

2. X.25 Packet Data Systems

X.25 packet data systems have been in existence for years. They wereinitially used for commercial dedicated network communications that weretypically fixed point to fixed point in nature. The X.25 protocol is aCCITT packet protocol that has multiple layers and was originallydesigned for a wireline environment. It was adapted some years ago forthe wireless environment and with some modifications has permittedpackets to be sent with greater reliability in the wireless environment.The above-identified patents disclose a modification of the X.25protocol. The primary difference between a wireless X.25 protocol and awireline X.25 protocol is the fact that additional error correction asdescribed above must be added to the wireless packets to increase thereliability of transmission. As the packet protocol is serial in nature,as much as fifty percent of the data transmitted pertains to errorcorrection in an attempt to minimize the amount of packet retransmissionthat could occur when packets were improperly received at thedestination. However, even with the added error correction, it becameapparent that the fixed transmitting stations and the mobile equipmenthas to incorporate an added complexity in construction in an attempt todirectly address the retransmission phenomenon when packets wereimproperly received by the destination equipment. This added complexityis in the form of additional processing equipment that has had to belocated at fixed stations and also within the mobile equipment. Therehave been numerous permutations of additional equipment that are needed.It consists generally of added processing hardware which must store thereceived data message and then provide a degree of testing to insurethat all of the information that was sent in the transmission wasproperly received. As data messages continue to increase in length, thecomplexity of the processing has increased correspondingly so that onlyportions of the received message would be retransmitted in the event oferrors. The X.25 packets are divided into frames with each frametypically consisting of two hundred fifty-five characters. An error inan X.25 packet requires retransmission of the whole packet which addssubstantial inefficiency to the data throughput.

If frame eight of a ten frame message contains an error, the receivingtransceiving unit must wait until the entire packet is received. Thenthe receiving transceiving unit requests from the originatingtransceiver that frame number eight be retransmitted to the receivingtransceiving unit. Retransmission of frame eight follows which leads tosubstantial overhead lowering the effective data throughput.

Regardless of the exact configuration of the equipment, it can be seenthat an added complexity in the receiving/transceiving circuitry isneeded to store the message during the evaluation process and to havethe ability to request a retransmission of erroneous data. The entiremessage must be stored and then await for the erroneous data to bereplaced in a new packet.

Not only is the complexity of the receiving/transceiving circuitryincreased, the originator of the packet message also has a correspondingincrease in equipment complexity. The originating transmitting facilityassociated with a base station has to store the entire message of tenframes of twenty five hundred characters and then hold that messageuntil it receives verification from the receiving/transceiving unit or arequest for missing frames of the transmitted information. Assuming thatmany data messages are constantly being processed and transmitted tomany different transceivers, the complexity of the processing equipmentat the data message originating end increases dramatically. In terms ofair time efficiency, this retransmission of packets serves to reduce thenumbers of subscribers that a two-way data mobile system is capable ofaccommodating.

Some of the wireless carriers have aligned with the European MPT1327protocol. There are numerous permutations of this protocol each havingdifferent identifying numbers. The overall theory of operation remainsessentially the same for each. It is a form of fast frequency shiftkeying (FFSK) that is utilized on narrow band radio channels. The MPTprotocol in its most typical application is similar to that of many SMRsystems. There is typically a setup channel and a number of workingchannels. The structure of the MPT protocol is such that it is similarto the one-way POCSAG protocol discussed above (CCIR radio paging codenumber one). The MPT protocol like the POCSAG protocol, issemi-synchronous in nature with time slots that can be allocated formessages to be sent to specific mobiles. The control channel isresponsible for the tracking control of the mobile data units. The MPTprotocol has the ability to handle voice as well as data transmissions.When voice or extended data transmissions are required, the mobile issent to a traffic channel.

As discussed above regarding the X.25 protocol, the same complexitiesfor both the receiving and transmitting transceiver are required for theMPT protocol to insure the reliable transmission of information whenerroneous data transmissions occur. Essentially, the system must requesta retransmission of the missing data which in turn lowers the throughputefficiency of the data system dramatically and therefore, lowers thenumber of subscribers that may be accommodated accordingly.

The European MPT protocol with its 63,48 cyclic code can tolerate bitfade error with varying results.

The more bit errors that are tolerated (five bits maximum or 4.166milliseconds) the greater the probability of an erroneous data characterwill be received that could cause a problem. If the error occurs duringthe ID code or a channel change command, the result is a catastrophicloss in communications.

If the number of tolerable error bits are decreased to one or two bits,the decoding reliability increases considerably. However, the fadetolerance suffers a corresponding decrease (eight hundred thirty-threeand sixteen hundred sixty-six microseconds respectively).

The MPT protocol is gaining an increased popularity for dispatchgovernment, political, law enforcement, fire department and numerousother two-way radio data services that need both short data and analogcommunications. A loss of message or erroneous data characters can haveserious consequences in an emergency situation. A wrong address todispatch a fire truck or ambulance can cause a life threateningsituation. A missed message from a police officer or a need for helpsituation can be fatal.

The semi-synchronous nature of the MPT protocol affords little tolerancefor error correction of the data from the fading environment.

3. Cellular Data Systems

Cellular radio has an ability to address data services which is similarto the previously described two-way systems. Cellular operatingfrequencies are wideband in nature and permit both voice and data to betransmitted on a working channel. Much like the MPT protocol, cellularhas a setup channel that communicates in a data only fashion to all ofthe mobiles that reside within a cell. This setup channel is responsiblefor keeping track of mobiles. Cellular systems have a data rate ofapproximately ten kilobaud that communicates to the cellular mobileunits. The cellular system protocol is synchronous in nature andtransmits data in a serial fashion.

Cellular radio systems have a similar problem that is experienced whenfades occur during a transmission to a mobile that wishes to place orreceive a call. The call setup process is aborted when bit error occursduring call setup. This typically gives the cellular mobile user asystem busy response. In the case where a land to cellular mobile callis being attempted, the receipt of erroneous data precipitates a "mobileout of range" or "message to be received by the telephone party".

During a cellular mobile telephone call, the mobile is directed to aworking channel by data sent to the mobile from the setup channel. Oncethe mobile is placed on a working channel, the voice conversation canbegin and due to the wide operating bandwidth of the channel, both thevoice conversation between three hundred and three thousand hertz canoccur as well as ten kilobaud data stream that permits data to be sentfrom the mobile to the system or visa versa.

The amount of data that is sent on the cellular working channel istypically minimal. From the cellular system to the mobile, data istypically sent concerning a call hand off or an increase/decrease inoperating power. When this information is subject to a fade thatprecipitates the loss of data, the mobile will either fail orerroneously change its power correspondingly resulting in a noisyconversation or cellular hand off information that is incorrectlyreceived and a catastrophic failure with loss of call results.

4. Data Service Air Time Inefficiencies

Research by G. Cromack of Cromack Industries has indicated that theprobability for data error increases when more data bits in a messageare dedicated for error correction. The theoretical throughput isapproximately eighteen percent for a mobile data communication's system.In reality, the data throughput of the mobile system can be as low asten percent. This low throughput rate is due to a number of factors thatrelate to the design of the protocol utilized, and is in part,indirectly caused by the lack of robustness of the protocol to resistthe effects of radio fading. In order to increase the efficiency andprobability of reliable mobile data communications, the robustness ofthe protocol to resist fading of the data must be improvedsignificantly.

5. Data Service Problematic Areas

Basically there are four distinct problematic areas that need to beaddressed and the problems resolved to provide a substantial increase inair time efficiency. The four problematic areas serve to collectivelycombine to reduce the overall operating efficiency of a mobile dataservice. They are as follows:

a. Data Message Reliability

All of the current prior art data services are serial in format. Thereneeds to be an improvement in the transmission of serial data thateliminates erroneous characters from being received. The primary causeof erroneously received characters is due to the phenomenon of fading.Fading for purposes of this explanation, as generally discussed above,is defined as any form of natural or man-made phenomenon that causes themedian signal level to drop below that of the receiving circuitry'sthreshold receiving level. This fading could be caused by the effect ofRayleigh fading, multipath reception and waveform distortions caused byman-made or natural noises. The net effect of a fade is such that thereceiver, transceiver or receiving circuitry associated with a basestation experiences either an erroneous or lost character or, in a worstcase, the loss of an entire message because of loss of synchronism. Thefading phenomena takes place at all radio frequencies.

The cumulative effects of fading serve to substantially decrease airtime efficiency of a mobile data channel. It first causes a mobile torequest the retransmission of additional data that was missed orerroneously received due to the fade. Many of the serial protocolstransmit blocks of characters that are two hundred fifty-five characterseach. Even though there may only be five or six erroneous characters,the entire block of two hundred and fifty-five characters must be resentto the mobile. Additional air time is consumed by the mobiles requestfor retransmission of data, thereby making the radio channel unavailableto other mobile data units. The problem is further aggravated by theincreased number of transmissions from mobiles requesting missing blocksof transmission of data to be retransmitted and the probability formobile transmission collisions increases considerably. It is thecollective combination of the added air time for the retransmission ofmissing data that typically requires a much greater number of charactersto be retransmitted than the few missing characters, additional air timedelays during transmissions, and the potential for additional collisionsto occur, that cumulatively reduce the air time efficiency.

b. Increased Data Speed on Narrow Band Channels

Many of the serial digital data protocols transmit data at 1200 baud(subcarrier 1200 Hz.). At 1200 baud (or 1200 BPS), the actual datathroughput speed when the number of error correction bits and otheroverheads are taken into account makes the data bit transmission ratevery slow. This effectively reduces the number of mobile data units thatcan reside on an individual channel. In order to increase the number ofmobile data units on the existing radio infrastructure, higher speeddata protocols need to be implemented. The constraints of the currentnarrow bandwidth channels are such that a transmission philosophy mustbe compatible with the current bandwidth requirements to permit a highspeed protocol to be implemented. If a data speed increase could beachieved, the number of mobile units that reside on a data channel couldbe increased correspondingly.

c. Median Field Strength

The median field strength for most data services is typicallyforty-three dbu. This corresponds approximately to 130 microvolts permeter of radio field strength. This field strength requirement is topermit a 95% reliability in the transmission and reception of datamessages. This poses a problem with the current infrastructure in thatto serve a metropolitan area, numerous radio transmitters and receiversare required to provide service. When multiple channels and a dataservice are accommodated, it becomes apparent that large numbers ofradio transmitter receivers are required to provide reliable service ina metropolitan area. Techniques should be evaluated to reduce the numberof radio transmitters necessary to provide reliable data service in ametropolitan area. If the median field strength can be reduced byone-half (e.g. three dbu), the number of transmitters can be reducedproportionately. Therefore any technological advance that could reducethe number of radio transmitters to provide such a data service has anet result in reducing capital plant equipment cost to the data servicecompany, with a corresponding decrease in cost of service to the enddata user.

d. Battery Consumption

Current mobile services are not sensitive to consumption of batterycurrent. The electronics to process the receiving and transmitting ofdata messages have little impact on a vehicular transceiver that has anautomotive battery at its disposal. However, there is a move in theindustry towards increased portability and downsizing of verysophisticated computer products. Computers have progressed fromtwenty-five pound desktop devices to easily portable devices. Computersthat are now this mobile and portable have a tremendous requirement forthe receipt of wireless data. They are no longer confined to a desktopor dedicated telephone line to receive or transmit data information.However, with the downsizing and portability of these computer products,the battery power available for two-way transmission services becomescritical. The power output of the transceiver needs to be minimized inorder to conserve battery life. More importantly, in order to gain thegreatest savings in battery efficiency, the number of retransmissions toreceive missed data must be reduced as much as possible. The previouslydescribed data speeds, field strength requirements, and robustness ofthe data protocol become critical factors to accommodate the portabledevices which are anticipated to be introduced into the wirelessmarketplace.

The analysis of error rates described above with reference to one-waywireless communications involving digital protocols, such as POCSAG, isequally applicable to two-way wireless communications. Atmosphericfading causes two-way wireless systems to experience the same types oferrors in transmissions between message originating transceivers andreceiving circuitry associated with base stations (uplink) andtransmissions between transmitters located at base stations (downlink)and message receiving transceivers as occur in one-way communicationsystems between a transmitter and a receiver.

DISCLOSURE OF INVENTION

The present invention is an improved one- and two-way method of wirelessserial transmission of information subject to fading. The inventionfurther is improved receiving circuitry used in receivers andtransceivers and in association with base stations for reception ofwireless serial transmissions of information subject to fading andimproved transmitting circuitry used in transmitters, transceivers andin association with base stations for wireless transmission of serialinformation. The invention lessens erroneous information transmissioncaused by atmospheric fading by permitting error recovery andreconstruction of erroneous information which may not be corrected witherror correction code contained in frames of the transmittedinformation, resynchronizes the clock of the receiving circuitry oftransceivers and receivers and associated with base stations after theoriginal receiving circuitry clock synchronism is lost. The inventionalso requires less radiated power than prior art one-way and two-waywireless systems to transmit serial information because of its errorrecovery, reconstruction and resynchronization capabilities.

First, the invention provides error recovery and reconstruction of datain frames comprised of data and error correction code bits consequentfrom the receiving circuitry using at least one processor (preferably adigital signal processor) to detect the presence of and position oferroneous uncorrectable bits within the frame in the circumstance whenthe bit error correction capacity of the error correction code isexceeded and, thereafter, processing the frames containing at least oneerroneous uncorrectable bit to selectively reconstruct valid datatherein which would be rendered erroneous when only error correctioncode processing is utilized to correct transmission errors. Thecomputation by the at least one processor that a frame contains a numberof bit errors exceeding the error correction capability of the errorcorrection code of a frame (e.g. 3) is used to initialize a process ofanalyzing the bits of the complete frame including the data and errorcorrection code bits to recognize a pattern of successive bit valuesrepresentative of erroneous uncorrectable bits (e.g. all ones or allzeros) greater in number than the error correction code's bit correctioncapacity, which is typically two bits. Then a determination is made ifthat pattern of erroneous uncorrectable bits is totally within the errorcorrection code bit field, which is indicative that the bits which arenot within the bit field of the error correction code, are recoverableand valid.

Second, the invention permits resynchronization of the clock of thereceiving circuitry after the original synchronization is lost bytransmitting a synchronization marker contained within a frame grouprepresentative of an invalid data unit (e.g. 11000000 when extended asASCII characters are being transmitted). Each frame group has at leastone and preferably a plurality of frames with each frame being comprisedof a plurality of data bits (e.g. 24) and a plurality of errorcorrection code bits (e.g. 21) in the form, for example, of a 45, 21 BCHframe. Once one or more sequential frames are processed using the errorcorrection code therein to determine that at least one frame has atleast one erroneous uncorrectable bit, the processor of the receivingcircuitry has determined the receiving circuitry's clock has lost itsoriginal synchronization. Thereafter, the at least one processorsearches the stored detected bits of the frames using known techniquessuch as shifting of the bits stored in memory to detect and locate asynchronization marker transmitted in time after the at least one framewhich has been determined to contain at least one erroneousuncorrectable bit. Location of the synchronization marker resynchronizesthe clock of the receiving circuitry. A determination that the detectedsynchronism marker, which was transmitted after the transmission of theat least one frame containing the at least one erroneous uncorrectablebit, is within the transmission of the frames of information isconfirmed by the at least one processor comparing a frame group addressof a frame group containing one or more frames containing the at leastone erroneous uncorrectable bit and a frame group address of asubsequently transmitted frame group containing the detectedsynchronization marker which is preferably a first frame group detectedhaving a synchronization marker. The frame group address identifies aunique address of each frame group within a plurality of frame groups.Each frame group preferably contains a plurality of frames eachincluding other bits which may encode for, example, data, identificationinformation of the receiving circuitry and commands to be executed bythe receiving circuitry and error correction code bits, thesynchronization marker and the frame group address.

The frame group address of the frame group containing the detectedsynchronization marker is used to locate the synchronization markeraddress relative to the at least one frame containing the at least oneerroneous uncorrectable bit. The frames which should be reconstructedafter clock resynchronization include the frame(s) containing the atleast one erroneous uncorrectable bit located by processing the errorcorrection code, as described above, within the frame group containingthe detected synchronization marker. Reconstruction processing of theseframes permits recovery of valid data which would have been lost withthe prior art's reliance on error correction code processing to correcttransmission errors. The reconstruction process involves reprocessingeach of the located frames first by determining if the frames containvalid bits outside the error correction bit field by processing theframes with the error correction code to determine if there are anyerroneous uncorrectable bits in the frames and if no erroneousuncorrectable bits are present in the bits outside the error correctionfield, the bits outside the error correction field are stored as validbits and the error correction code bits are discarded. Second, when theframes contain at least one erroneous and uncorrectable data bitdetermined from processing of the error correction code therein, adetermination is made if the bits outside the error correction field arevalid by locating where a pattern of a number of sequential bits of asingle value (all zeros or all ones) are located in the frame with thenumber of sequential bits being greater than the error correctioncapacity of the error correction code. Bits outside the error correctioncode bit field are valid only when the pattern of all zeros or ones islocated totally in the bit field of the error correction code. The validbits are stored and the error correction code bit field bits arediscarded and the invalid bits outside the error correction code bitfield are marked by an error character and the error correction codebits are discarded.

As a result with the present invention, frames transmitted after thetime of the fade causing the original clock synchronism to be lost untilthe end of the transmission of the frames of information arereconstructed after resynchronizing of the bit timing between thetransmitter and receiver circuitry clock which would be permanently lostwith prior art techniques. The reconstruction processing of the dataframes, after resynchronizing the receiving circuitry, may be performedin either the forward or backward directions as determined by addressesof the frame groups containing the frames to be reconstructed.Consequently, frames transmitted both before and after the detectedsynchronization marker which resynchronizes the clock of the receivingcircuitry are synchronously processed to recover and reconstruct validdata which in the prior art would have been lost because of loss ofclock synchronism which terminated reception producing an unacceptablyhigh data transmission error rate.

Less radiated power is required with the invention to transmit datawithout significant error than in the prior art. Fewer transmitters arerequired by the invention when compared to the prior art in ageographical area to provide a sufficiently strong electrical fieldrequired for a reliable low error rate data transmission as a result ofreconstruction of frames containing at least one erroneous uncorrectablebit and to resynchronization of the receiving circuitry clock andthereafter, reconstruction of frames to recover valid data which wouldhave been lost without resynchronization. The net effect of theinvention on data reception is that the receiving circuitry clock isresynchronized with the transmitter for all fades except those fadeswhich occur in the identification frame group which can prevent theidentification by the receiving circuitry of its identification numberin the information transmission and those fades which continue throughand end of the information transmission described below.

In a wide area coverage system or a national system, savings ininfrastructure resulting from requiring fewer base stations, etc. cansave tens of millions of dollars per system. The reduction ininfrastructure cost may be the difference between a data transmittingsystem being economical or uneconomical.

Faded information is any information or information units such as bits,bytes, or digital words caused by fading or other interference which areerroneous as a consequence of the serial information wirelesstransmission between the transmitting and receiving circuitry.

Erroneous uncorrectable bits are bits in frames which may not becorrected with error correction code contained in the frames. Fading ofinformation may cause the receiving circuitry to output erroneousuncorrectable bits because of the loss of receiving circuitry clocktiming.

As used herein, transmitting circuitry is circuitry associated with atransmitter, a base station or a transceiver which modulates the carrierwith a subcarrier and modulates the subcarrier with serially encodedinformation to be wirelessly transmitted serially to receivingcircuitry. Transmitting circuitry used for practicing the invention hasmany different and diverse possible forms.

As used herein, receiving circuitry is circuitry used in a receiver,transceiver switch or processor associated with a base station, etc.which detects the carrier, demodulates the subcarrier and processes thedemodulated information which was modulated on the subcarrier in anencoded serial format by the transmitting circuitry. Receiving circuitryused for practicing the present invention has many different and diversepossible forms.

Individual cycles of a subcarrier may each respectively be modulated tocontain part of a number of bits which make up each unit of transmittedinformation or data, such as the example below describing modulation ofthe squarewave subcarrier to encode individual eight bit characters intotwo sequential four bit nibbles which sequentially modulate halves ofthe same cycle of the subcarrier to encode the individual character orsuch as the example below describing modulation of a subcarrier havingindividual eight bit characters into sequential four bit nibblesmodulated at discrete angular positions of two sequential cycles of thesubcarrier. Alternatively, the individual modulated cycles of thesubcarrier may each contain at least one complete unit of information ordata such as an eight bit ASCII character.

The present invention has substantial advantages over the prior art datatransmission protocols such as, but not limited to the POCSAG and themodified ERMES protocols. Serial information transmission is made withfewer transmission errors, at a higher data throughput rate with thetransmission requiring less radiated power than with the prior art. Withrespect to the POCSAG protocol, the present invention will provideinformation transmission throughput rates which will be approximately anorder of magnitude or more higher and an error rate which will be lowerwhile not requiring substantial modification to the existinginfrastructure. The invention may use approximately one quarter theradiated power level of the POCSAG protocol. Similarly, with respect tothe modified ERMES protocol, the present invention will provide a higherdata throughput rate with a lower error data rate with a much greaterresistance to loss of synchronism caused by fading while requiring lessradiated power requiring fewer base stations. Furthermore, the presentinvention will permit resynchronization of the clock of the receivingcircuitry during the reception of the frames of information, which isnot possible with any of the prior art protocols discussed above.

The present invention shares many of the same improved performancecharacteristics of the data transmission system which is the subjectmatter of the above-referenced patent application Ser. Nos. 07/850,275,07/850,276, and 07/850,487 now abandoned and 08/112,256 now U.S. Pat.No. 5,446,759. As a consequence of the present invention transmittingthe information in a serial format instead of as two parallel streams,as described in the above-identified applications, it will have twicethe information transmission rate achieved by the data transmissionsystem of the above-referenced patent application Ser. Nos. 07/850,275,07/850,276, 07/850,487 and 08/112,256 without reliance on replacement offrames containing erroneous data with frames which are time offset fromthe faded frames that do not contain erroneous data as disclosed in theabove-identified applications.

The invention provides wireless one or two-way transmission ofinformation at high data rates even on channels such as on narrow bandchannels used for paging having 5 KHz FM deviation channel limits. Withthe invention, resynchronization is achieved between the broadcastserial information modulated on the subcarrier and the receivingcircuitry even when atmospheric fades occur of a duration up to orgreater than 400 milliseconds which is not possible with the prior artPOCSAG protocol which has limited fade resistance representing a two-biterror or less which is typically two to four milliseconds and noresynchronization capability and the prior art modified ERMES protocolwhich has a fade resistance up to approximately fourteen millisecondsand no resynchronization capability.

In one preferred embodiment of the invention, quadrants of cycles of asinusoidal subcarrier are modulated with the serial bits of theinformation and in another preferred embodiment, a squarewave subcarrieris pulse width modulated with different pulse widths representative ofdifferent numeric values representative of bit groups encoding theserial information. These preferred subcarrier modulation techniques ofthe present invention provide for a greater amount of information to bemodulated on each cycle of the subcarrier than with conventional digitalmodulation which provides for a single bit per half a cycle of thesubcarrier and with the ERMES and modified ERMES protocols which arelimited to four bits per cycle of the subcarrier. With the presentinvention, much higher data throughputs with a lower error rate areachievable on narrow data channels such as those channel bandwidths ofthe 150, 220, 450, 800, and 900 MHz. and above. For example, with a 2400cycle sinusoidal subcarrier, data bit modulation rates of 19 KHz. arepredictably achievable when processed with at least one digital signalprocessor as described below which optimizes the detection of datamodulated on the subcarrier, as well as the reconstruction of framescontaining erroneous uncorrectable data bits when processed with errorcorrection codes and resynchronization of the receiving circuitry clockwhen a major fade occurs causing the transmitting and receivingcircuitry to loose synchronization followed by the aforementionedreconstruction of frames.

The present invention uses conventional error correction codes such as,but not limited to, the BCH error correction code to correct minor biterrors in each of the frames detected by the receiving circuitry in theconventional manner. However, the receiving circuitry of the presentinvention when an uncorrectable error bit is detected in a framecontaining other bits and error correction code bits, such as athree-bit error in the prior art POCSAG protocol which is substantialenough not be corrected by the error correction code and representsfaded information which may cause synchronization to be lost between thetransmitting circuitry and the clock of the receiving circuitry, outputsthe received information with reconstructed frames having less errorthan achievable with the use of error correction code and whennecessary, as determined by processing of the error correction code ofthe frames of information to detect one or more frames each containingat least one erroneous uncorrectable bit error and resynchronizes theclock of the receiving circuitry by locating a synchronization markertransmitted within a frame group. Resynchronization of the receivingcircuitry clock permits the detected stored frames decoded by thereceiving circuitry to be synchronously processed with thereconstruction technique of the invention to recover valid data whichoriginally could not be processed reliably because of the loss ofsynchronism. Reconstruction of valid data bits after resynchronizationis performed when (1) the error correction code correction capacity ofthe frames is not exceeded or when (2) the erroneous uncorrectable bitsare determined to be totally within the error correction code bit fieldof a frame which is the condition required to reconstruct valid data inthe presence of at least one uncorrectable bit error in a frame.

The present invention uses the pattern recognition capability of adigital signal processor to determine where in a frame at least oneerroneous uncorrectable bit error exists. Valid data is reconstructedfrom a frame and stored in memory while discarding the error correctioncode bits of the frame when a pattern of erroneous bits in the form of anumber of successive zeros or a number of successive ones containedtotally within the bit field of the error correction code is detectedwith the number being greater than the bit error correction capacity ofthe error correction code. If any bits within the pattern of successiveones or zeros are located outside of the bit field of the errorcorrection code, the data of the frame is considered invalidnecessitating the storage in memory of the receiving circuitry of anerror marker.

The at least one digital signal processor of the receiving circuitryprovides for enhanced signal to noise response consequent from signalprocessing of the analog or digital subcarrier. The digital signalprocessing provides for extremely high speed integration of themodulated subcarrier which sums the energy encoding the modulated dataon the subcarrier to produce highly accurate detection of the data. Thedetected individual cycles of the subcarrier are processed to calculatean integral of at least one selected modulated part of each of theindividual cycles (e.g. one half of a pulse width modulated cycle of asquarewave subcarrier or an angular window centered on discrete spacedapart angular positions of an analog subcarrier). The integral isnumerically compared with a plurality of stored numerical ranges whichranges each represent one of a plurality of possible numerical valuesthat the selected part may encode to identify a stored range numericallyincluding the calculated integral and substituting for the at least oneselected part of each of the cycles the one of the plurality ofnumerical values representative of the identified stored range includingthe calculated integral with each numerical value encoding at least bitof the frames of the information. The numerical values may be that of asingle bit or groups of bits.

The digital signal processor further processes the detected individualcycles of the subcarrier to further calculate the integral by taking aplurality of samples of each selected modulated part of each of theindividual cycles with each sample having a numerical value and eachsample is compared with a range of numerical values representing a validsample which should be included within the calculation of the integraland when the comparison reveals that the sample value is outside therange of the numerical values, the compared value is replaced with avalue which is a function of the sample values adjacent the sample valuewhich is replaced. The compared value is replaced with a value which isfunction of the values adjacent the sample value which is replaced.Preferably, the compared sample value is replaced with a value which isan average of the at least one sample value which precedes the samplevalue and the at least one sample value which succeeds the comparedsample value.

Transmitting circuitry in accordance with the invention includes anencoder for modulating a subcarrier with at least one identificationframe group which identifies receiving circuitry to receive theinformation followed by at least one data frame group, eachidentification frame group comprising a plurality of frames with atleast one of the plurality of frames of the identification frame groupcontaining bits identifying the receiving circuitry to receive a radiofrequency carrier, a plurality of bits of error correction code in eachframe, synchronization information for originally synchronizing a clockof the receiving circuitry and a synchronization marker comprised of aplurality of bits which do not represent valid data for resynchronizingthe clock of the receiving circuitry, each data frame group having aplurality of frames each including a plurality of bits of errorcorrection code and a plurality of bits of data, and anothersynchronization marker comprised of a plurality of bits which do notrepresent valid data for resynchronizing the clock of the receivingcircuitry; a modulator, coupled to the encoder, for modulating a radiofrequency carrier with the subcarrier; and a transmitter, coupled to themodulator, for wirelessly transmitting the modulated carrier. Each framegroup contains a frame group address comprised of a plurality of bitswhich identify a unique address of the frame group within the pluralityof frames of wirelessly transmitted information. Cycles of thesubcarrier are modulated by the encoder with pulse width modulation witha width of parts of the subcarrier being modulated with at least one bitof the frames of the information or cycles of the subcarrier aremodulated by the encoder with bits encoding the plurality of frames ofinformation with each cycle of the subcarrier being modulated by bits ata plurality of separated angular positions. The synchronizationinformation also includes bits identifying the receiving circuitry. Theidentification frame group also contains a command field containing atleast one bit for commanding a function to be performed by the receivingcircuitry.

Transmitting circuitry in accordance with the invention includes anencoder for modulating a subcarrier with at least one frame groupcomprising synchronization information for originally synchronizing aclock of receiving circuitry to receive the frames of the informationwith each frame group comprising at least one frame with each framecomprising a plurality of bits of error correction code and a pluralityof other bits, and a synchronization marker comprised of a plurality ofbits which do not represent valid data for resynchronizing the clock ofthe receiving circuitry after initial synchronization of the clock byreception of the synchronization information; a modulator, coupled tothe encoder, for modulating a radio frequency carrier with a subcarrier;and a transmitter, coupled to the modulator, for wirelessly transmittingthe modulated carrier. Each frame group contains a frame group addresscomprised of a plurality of bits which identify a unique address of theframe group within the plurality of frames of wirelessly transmittedinformation. Cycles of the subcarrier are modulated with pulse widthmodulation with a width of parts of the subcarrier being modulated withat least one bit of the frames of information or cycles of thesubcarrier are modulated by the encoder with bits encoding a pluralityof frames of information with each cycle of the subcarrier beingmodulated by bits at a plurality of separated angular positions. The atleast one frame group also contains a command field containing at leastone bit for commanding a function to be performed by the receivingcircuitry.

A process for transmission of a plurality of frames of information inaccordance with the invention comprises modulating a subcarrier with atleast one identification frame group which identifies receivingcircuitry to receive the information followed by at least one data framegroup, each identification frame group comprising a plurality of frameswith at least one of the plurality of frames of the identification framegroup containing bits identifying the receiving circuitry to receive theradio frequency carrier, a plurality of bits of error correction code ineach frame, synchronization information for originally synchronizing aclock of the receiving circuitry and a synchronization marker comprisedof a plurality of bits which do not represent valid data forresynchronizing the clock of the receiving circuitry, each data framegroup having a plurality of frames each including a plurality of bits oferror correction code and a plurality of bits of data, and anothersynchronization marker comprised of a plurality of bits which do notrepresent valid data for resynchronizing the clock of the receivingcircuitry; and modulating the radio frequency carrier with thesubcarrier and wirelessly transmitting the modulated carrier. Each framecontains a frame group address comprised of a plurality of bits whichidentify a unique address of the frame group within the plurality offrames of wirelessly transmitted information. Cycles of the subcarrierare modulated with pulse width modulation with a width of parts of thesubcarrier being modulated with at least one bit of the frames ofinformation or cycles of the subcarrier are modulated with bits encodingthe plurality of frames of information with each cycle of the subcarrierbeing modulated by bits at a plurality of separated positions. Thesynchronization information also contains bits identifying the receivingcircuitry. The identification frame group also contains a command fieldcontaining at least one bit for commanding a function to be performed bythe receiving circuitry.

A process for transmitting a plurality of frames of information inaccordance with the invention includes modulating a subcarrier with atleast one frame group comprising synchronization information fororiginally synchronizing a clock of receiving circuitry to receive theframes of the information, each frame group comprising at least oneframe with each frame comprising a plurality of bits of error correctioncode and a plurality of other bits in a synchronization marker comprisedof a plurality of bits which do not represent valid data forresynchronizing the clock of the receiving circuitry after initialsynchronization of the clock by reception of the synchronizationinformation; and modulating a radio frequency carrier with the modulatedsubcarrier and wirelessly transmitting the modulated carrier. Each framegroup contains a frame group address comprised of a plurality of bitswhich identify a unique address of the frame group within the pluralityof frames of wirelessly transmitted information. Cycles of thesubcarrier are modulated with pulse width modulation with a width ofparts of the subcarrier being modulated with at least one bit of theframes of information or cycles of the subcarrier are modulated withbits encoding the plurality of frames of information with each cycle ofthe subcarrier being modulated by bits at a plurality of separatedangular positions. The at least one frame group also contains a commandfield containing at least one bit for commanding a function to beperformed by the receiving circuitry.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a diagram of the prior art POCSAG protocol.

FIG. 2 illustrates a diagram of a typical seven digit numerical pageusing the POCSAG protocol.

FIG. 3 illustrates numeric POCSAG protocol transmissions.

FIG. 4 illustrates a block diagram of a prior art processor and protocolencoder.

FIGS. 5A-C illustrate frame groups of frames of information formattedfor serial wireless transmission in accordance with the presentinvention and FIG. 5D illustrates an alternative frame group of frameswhich may be used to send a smaller number of frames of information thanwith the frame groups of FIGS. 5A-C.

FIGS. 6A and 6B respectively illustrate a sinusoidal subcarrier and asquarewave subcarrier modulated with phase and pulse width modulationencoding the serial information of FIGS. 5A-D.

FIG. 7 illustrates a block diagram of a one-way information transmissionsystem in accordance with the present invention.

FIG. 8 illustrates the modulation of the sinusoidal subcarrier toproduce one form of the serial information encoded in accordance withthe present invention.

FIG. 9 illustrates pulse width modulation of the subcarrier to produceanother form of the serial information encoded in accordance with thepresent invention.

FIG. 10 illustrates a block diagram of an example of a processor andprotocol encoder in accordance with the present invention.

FIG. 11 illustrates encoding controller system entries used inaccordance with the invention.

FIG. 12 illustrates a circuit schematic of the transmitting circuitry ofthe present invention.

FIG. 13 illustrates a circuit schematic of the receiver circuitry inaccordance with the present invention.

FIGS. 14A and B illustrate the integration of the detected modulatedsinusoidal subcarrier in accordance with FIG. 6A by the digital signalprocessor of the receiving circuitry of the present invention.

FIG. 15 illustrates the integration of the detected pulse widthmodulated subcarrier in accordance with FIG. 6B by the digital signalprocessor of the receiving circuitry of the present invention.

FIGS. 16A and 16B illustrate sample processing performed by the digitalsignal processor of the receiving circuitry to remove noise transientsin a pulse width modulated subcarrier in accordance with the presentinvention.

FIGS. 17A and 17B illustrate sample processing performed by the digitalsignal processor of the receiving circuitry to remove noise transientsin a phase modulated sinusoidal subcarrier in accordance with thepresent invention.

FIG. 18 is a flowchart of the operation of the digital signal processorof the receiving circuitry comparing integrals of the detectedsinusoidal or digital subcarriers with prestored ranges to convert theserial information modulated on the subcarrier into a series ofnumerical representations of at least parts of data units in the form ofindividual bits or groups of bits which are modulated on the subcarrierin accordance with the format of FIGS. 5A-C, 5D or modificationsthereof.

FIGS. 19A and 19B are a flowchart of the general operation of thereceiving circuitry in accordance with the present invention.

FIG. 20 is a block diagram of a two-way wireless informationtransmission system in accordance with the present invention.

FIG. 21 is a block diagram of a transceiver in accordance with thepresent invention.

FIG. 22 illustrates a valid bit pattern of the DATA FRAME GROUP of FIG.5B including the marker S" and FRAME GROUP #.

FIGS. 23-25 illustrate examples of bit patterns of frames in accordancewith the frame groups of FIGS. 5A-C containing erroneous uncorrectablebits that are processed by the digital signal processor of the receivingcircuitry to attempt to reconstruct valid data which cannot be recoveredby processing the frames with only the error correction code.

FIGS. 26A-C illustrate a flow chart of the processing performed by thedigital signal processor of the receiving circuitry to reconstruct datawithin frames containing at least one erroneous uncorrectable bit, toresynchronize the clock of the receiving circuitry to synchronizeprocessing of the frames of the frame groups of FIGS. 5A-C and afterresynchronization to reconstruct frames beginning with the frames whichwere previously tested with the error correction code and determined tohave at least one erroneous uncorrectable bit and continuing through theframes of the frame group containing the detailed synchronizationmarker.

FIG. 27 illustrates the processing of detected stored frame groups toresynchronize the clock of the receiving circuitry in accordance withthe present invention.

Like reference numerals identify like parts throughout the drawings.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is an improved one-way and two-way wireless serialinformation communication system and method of operation thereof havinga higher data transmission rate, a lower error rate and requiring lowerrequired radiated power than prior art one-way and two-way serialcommunication systems. The invention further is improved transmittingand receiving circuitry and a method of operation thereof for wirelesstransmission of serially encoded information.

The present invention provides reconstruction of data detected with thereceiving circuitry which has been rendered erroneous by fading causingbit errors beyond the bit error correction capacity of error correctioncode contained in frames of information such as the BCH error correctioncode used in the prior art. The error correction code of each frame isprocessed with at least one processor, which preferably is a digitalsignal processor, to detect and analyze where erroneous uncorrectablebits are present in each frame which cannot be corrected using errorcorrection code to permit reconstruction of valid bits outside the bitfield of the error correction code where a bit pattern representative ofa fade (e.g. successive all zeros or all ones) of a number of bitsgreater in number than the bit error correction code capability of theerror correction code, such as two bits, is detected totally in theerror correction code bit field of the frame.

Furthermore, the present invention resynchronizes the clock of thereceiving circuitry after a series of one or more frames are determinedby processing with the error correction code therein to have at leastone erroneous uncorrectable bit which is representative of the detectedreceiving circuitry clock being out of synchronism with the subcarriertiming of the transmitting circuitry. Resynchronization of the clock ofthe receiving circuitry is accomplished by detecting a validsynchronization marker using known techniques, such as bit shifting inregisters or memory of the decoded serial information, which has beentransmitted after the one or more erroneous uncorrectable bits in atleast one frame which have been detected by processing the frame withthe error correction code contained therein. Resynchronization of thereceiving circuitry clock enables subsequent synchronous processing ofthe frames transmitted before the detected synchronization marker to beprocessed as part of the reconstruction process and synchronousprocessing of frames transmitted after the detected synchronizationmarker. The frame group address transmitted with each frame grouppermits determination of the number of frames transmitted before thedetected synchronization marker which must be processed as part of thereconstruction process occurring after resynchronization. All theframes, beginning with the at least one frame containing the at leastone erroneous uncorrectable bit through the frames in the frame groupcontaining the detected synchronization marker are again processed withthe error correction code and bits outside the bit field of the errorcorrection code are stored as valid bits and the bits of the errorcorrection code are discarded when the bit error correction capacity ofthe error correction code of the frames is not exceeded. Moreover, afterresynchronization, all of the reprocessed frames which are determined tocontain erroneous uncorrectable bits which are determined to have theerroneous uncorrectable bits totally within the bit field of the errorcorrection code have the bits outside the bit field of the errorcorrection code stored as valid bits. Finally, an error character isstored to mark the bits of frames outside the bit field of the errorcorrection code which cannot be reconstructed when one or more erroneousuncorrectable bits are determined to be outside the bit field of theerror correction code. Furthermore, normal synchronous processing isperformed of frames transmitted after the detected and synchronizationmarker resynchronizes the clock of the receiving circuitry includingreconstruction of those frames which are determined to contain at leastone erroneous uncorrectable bit. Conventional bit manipulationtechniques may be used to locate the synchronization marker required forresynchronization such as bit shifting in registers or memory.

FIGS. 5A-5C illustrate an example of a preferred serial encoding formatof information in accordance with the protocol of the present invention.The information is transmitted in time from left to right and from FIG.5A to FIG. 5C such that the ID FRAME GROUP is followed by one or moreDATA FRAME GROUPs, followed by the SHORTENED EOF FRAME GROUP. However,if the number of data units at the end of the transmission was one less(e.g. nine) than the total number of data units in the DATA FRAME GROUP(e.g. to ten) the EOF character could be placed in the data unitposition ten of the DATA FRAME GROUP which eliminates transmission ofthe SHORTENED EOF FRAME GROUP. Each wireless transmission of informationis typically comprised of three sequentially transmitted main blocks offrame groups respectively illustrated in FIGS. 5A-5C.

FIG. 5A illustrates the ID (identification) FRAME GROUP which iscomprised of at least four frames each comprised of forty five bits.Each frame is comprised of twenty one bits of error correction codepreferably of the BCH type. The bit groups "C" are respectivelyrepresentative of groups of ten and eleven bits of BCH code whichcomprise the total of twenty one bits of error correction code anddefine the bit field of the error correction code. The bits which arenot contained in the error correction code bit field are referred to asother bits. The preceding and remaining three bit groups each containgroups of eight bits. The first two eight bit groups each contain arepeat of eight bits of identification information each containing twofour-bit nibbles respectively encoding the first two digits of thereceiving circuitry identification which, along with the otheridentification nibbles three through fourteen, as illustrated,collectively uniquely identify the receiving circuitry to receive theinformation to be transmitted. The third eight bit group S' is astandard SYNC address well known in the art which performs the initialsynchronization of the clock of the receiving circuitry. The first framemay be repeated multiple times as indicated.

The S' and ID wake-up fields have multiple purposes. One aspect of theS'/ID fields is to permit the coexistence of the protocol of the presentinvention with other radio messaging protocols on the same radiochannel. Ninety-five percent of the current radio messaginginfrastructure utilized for paging has multiple messaging formats whichare intermixed in a non-time synchronized fashion. The protocol of thepresent invention, unlike the modified ERMES protocol, may coexist withother industry standard protocols without interference, and does notcause interference or degrade reception. The same benefit of theinvention also exists for its application to two-way wireless systems.

The S'/ID fields are binary serial data that permit the receivingcircuitry to detect that information which is contained in theinformation field is to be transmitted. The S' field has the first twodigits of the receiver's or transceiver's ID embedded into it. Thedigital signal processor of the receiving circuitry, as described below,detects and looks for a bit pattern match that matches its preprogrammedsynchronization and the first two ID digits of its identification code.When a match occurs, the receiving circuitry turns on the balance of itselectronics and begins the decoding process as described below. TheS'/ID fields utilize the first two digits of the receiver's ortransceiver's ID to provide as many as one hundred different groups ofreceivers or transceivers to be accommodated on the same radio channel.The net effect of the two digits of the identification code S' embeddedwithin the initial synchronization information is to provide asignificant battery savings to wireless receivers and transceivers. Onlythe group that is being signalled with the two digit ID match within thesynchronization field containing the first two digits of identificationinformation and S' is alerted resulting in the receiving circuitry beingturned on. All other receivers or transceivers, which include those inninety nine possible groups, will not detect a S'/ID digit match whichresults in the receiver or transceiver power consuming electronics notbeing turned on to save battery life which is significant with mobilereceivers and transceivers powered with small batteries.

The duration of the S'/ID wake-up fields is programmable on a customerbasis. The duration of the overall synchronization signal including thefirst two digits of the identification code of the receiving circuitryand S' is directly dependent upon the type of receiver or transceiverthat is being utilized on the system. Variations of durations may benecessary to accommodate receivers or transceivers of different designsas the decoder technology advances in accordance with the presentinvention. The duration of the overall synchronization signal may beapproximately 900 Ms. As higher data rates are achieved, this durationmay be shortened. The duration of the synchronization signal isdependent upon the channel sampling rate of the receiver or transceiver.If the receiver or transceiver must turn on (wake-up) once every 450 MS,and it requires two samples, then the minimum synchronization durationshould be approximately 900 MS. The wake-up duration is directlydependent upon the amount of battery current savings in the receiver ortransceiver that are desired. The more frequently the receivingcircuitry wakes up to sample the channel the greater impact upon thereceiver's or transceiver's battery life.

The next frame of the ID FRAME GROUP contains an eight bit command fieldCB which may contain commands to the individual receiving circuitry orto batches of receiving circuitry to perform specified functions. Thecommands may be diverse in function such as, but not limited to, thosedisclosed in the above-described United States patents. The framefurther includes four four-bit nibbles encoding identification digitsthree through six, which encode four additional digits of theidentification code of the receiving circuitry, which are contained inthe next two groups of eight bits followed by the two groups of ten andeleven bits making up the twenty one bits of error correction code asdescribed above.

The following frame is comprised of three eight bit groups of four bitnibbles encoding identification digits seven through twelve of theidentification code of the receiving circuitry.

The final frame of the ID FRAME GROUP is comprised of one eight bitgroup of two four bit nibbles of identification digits thirteen andfourteen encoding the final two digits of the identification code of thereceiving circuitry. The next eight bit group is a synchronizationmarker S" which is a unique pattern of eight bits which do not identifyvalid data such as an extended ASCII character 11000000 as describedbelow. The detection of synchronization marker S", after a number offrames containing one or more erroneous uncorrectable bits have beenidentified by processing the error correction code in the frames whichrepresents a loss of synchronization, provides the important function ofresynchronization of the clock of the receiving circuitry. The originalsynchronization is, as explained above, established by the initial twodigits of the identification code and S'. Typically, the synchronizationaddress S' has a different bit pattern than the synchronization markerS". Effectively, the synchronization marker S" locates and providescorrect clock timing to permit resynchronizing the clock of thereceiving circuitry's at least one processor to provide correct timingfor processing groups of forty five bits defining each frame from thepoint of loss of the original synchronization thru and after thedetection of the frame group containing a detected synchronizationmarker S". As is known, the loss of even a single clock cycle in thetiming of the decoding and processing of frames of bits by the receivingcircuitry renders the data totally erroneous. Following thesynchronization marker S" is a FRAME GROUP # comprised of eight bitswhich contains a unique address of the ID FRAME GROUP within theplurality of frames of wirelessly transmitted information comprising theoverall transmission. As will be discussed below, the FRAME GROUP # isused to locate the frames and bits which must be processed duringreconstruction by the digital signal processor after resynchronizationis established beginning with the frames where synchronization loss isfirst detected by at least one frame being processed to contain at leastone erroneous uncorrectable bit which cannot be corrected with errorcorrection code embedded in the frames to the frames of the frame groupcontaining the detected synchronization marker S". Frames within the IDFRAME GROUP may be reconstructed as described herein. In the ID FRAMEGROUP an erroneous uncorrectable bit in the identification field nibblesone through fourteen, which cannot be reconstructed by thereconstruction technique of the invention, as explained below, iscatastrophic and the entire transmission is erroneous. Thesynchronization marker S" and FRAME GROUP # cannot correct erroneousuncorrectable bits encoding identification digits one through fourteenbecause of their presence outside of the bit field of the errorcorrection code.

FIG. 5B illustrates the format of the one or more DATA FRAME GROUPScontained in the serial transmission of frames of information. Each DATAFRAME GROUP is comprised of four frames containing a total of 180 bitswith each frame containing forty five bits as illustrated. The DATAFRAME GROUPS are repeated sequentially to contain sufficient eight bitdata units in combination with the SHORTENED EOF (end of frame) FrameGroup of FIG. 5C described below to encode the entire transmissionregardless of the type of data being transmitted. It should be notedthat the choice of having three eight bit data units per frame of theDATA FRAME GROUP is to optimize the transmission of alphanumeric dataencoded in eight bit ASCII or other eight bit data encoding mechanism.However, the number of bits per frame of data in an ID FRAME GROUP, DATAFRAME GROUP and a SHORTENED EOF FRAME GROUP, as described below, may bevaried in accordance with the invention. The invention may be practicedwithout having multiple data units per frame in the DATA FRAME GROUP.The twenty four data bits or other number of bits per frame in a DATAFRAME GROUP may be subparts, define a single data unit or define morethan one data unit including fractional parts (e.g. one and one-halfdata units each comprised of sixteen bits). Each frame contains twentyone bits of error correction code, as described above, which ispreferably BCH code, broken down into ten and eleven bit groupsidentified, as described above, with the letter "C". The bits which arenot contained in the error correction code bit field are referred to asother bits. As is known, the error correction code bit field bits have avalue which is a function of the twenty four data bits. The errorcorrection code field bits will be identical only when all twenty fourdata bits are identical (e.g. when three data units, such as threecharacters, are repeated in different frames, the error correction codefor the identical data units encoding the characters is repeated in thedifferent frames). As illustrated, each DATA FRAME GROUP contains teneight bit data units which are identified in succeeding frames by thenumbers "1-10". The synchronization marker S" is identical in form andfunction to the synchronization marker S" as described above inconjunction with FIG. 5A and is comprised of eight bits which do notencode a valid unit. The detection of the synchronization marker S"performs the resynchronization function of the clock circuitry asdescribed above. The FRAME GROUP #is also identical to the FRAME GROUP #described above in conjunction with FIG. 5A and performs the function ofpermitting the identification of a number of frames which must bereconstructed from where one or more frames containing at least oneerroneous uncorrectable bit are detected which is representative of lossof synchronization of the clock of the receiving circuitry are locatedto where the synchronization marker S" is detected, as described below,for example, in conjunction with FIG. 27. The combination of thesynchronization marker S" and FRAME GROUP # in the DATA FRAME GROUPpermits data reconstruction after resynchronization as described below.

When a long transmission is made spanning several hundred bits of data,the number of DATA FRAME GROUPS is chosen to pack all of the bits withinthe DATA FRAME GROUP and the SHORTENED EOF FRAME GROUP as describedbelow. Each successive DATA FRAME GROUP has a FRAME GROUP # which is anaddress comprised of a plurality of bits which identify a unique addressof the DATA FRAME GROUP within the plurality of frames of informationwhich comprise the entire transmission. For example, if a transmissionis to be made containing 1608 bits, a total of twenty DATA FRAME GROUPSare required each containing a unique address encoded in the FRAME GROUP# which identifies and addresses the frames and data units therein ofeach DATA FRAME GROUP with an address different from the remainingframes and data units of the remaining DATA FRAME GROUPS and a SHORTENEDEOF FRAME GROUP containing one data unit. Usually, but not necessarily,the addresses in succeeding DATA FRAME GROUPS are in the form ofascending numbers which permit the at least one processor of thereceiving circuitry, as described below, to immediately determine if thedetection of a subsequent synchronization marker S" is within the sametransmission because the FRAME GROUP # address in the DATA FRAME GROUPcontaining the detected synchronization marker is not lower than anaddress of a DATA FRAME GROUP containing at least one frame in which oneor more erroneous uncorrectable bit errors are detected which isindicative at the outset of a loss of synchronization. If the detectedFRAME GROUP # address is lower, the least one processor determines thatthe fade has obliterated the remainder of the data transmission,including the SHORTENED EOF FRAME GROUP containing an end of messagecharacter or notation.

FIG. 5C illustrates a SHORTENED EOF (end of frame) GROUP which ispreferably used to end each transmission of information of the format ofFIGS. 5A-C. A single data unit comprised of eight bits, which isidentified by the symbol "X", contains the last eight data bits of thetransmission of the multiple frames of information. The following twogroups of one hundred twelve bits, which are identified by the legend"EOF" contain an eight bit end of file marker and one hundred four bitsof filler code. The error correction code identified by "C", asdescribed above, which comprises twenty one bits, is identical to theerror correction code of the ID and DATA FRAME GROUPS. The bits whichare not contained in the error correction code bit field are referred toas other bits.

Each transmission of data, regardless of what is being encoded (e.g.eight bit ASCII characters, sixteen bit graphics, etc.) is typicallyformatted by the at least one processor of the transmitting circuitry asexplained below into the format having the sequence of the ID FRAMEGROUP, the DATA FRAME GROUP(s), and the SHORTENED EOF FRAME GROUP. Ashas been stated above, the architecture of each frame of the DATA FRAMEGROUPS having three eight bit data units has been optimized for thetransmission of eight bit characters encoded with ASCII. However, thenumber of bits of data per frame, and the number of bits of errorcorrection code in each of the FRAME GROUPS may be varied whilepracticing the invention.

FIG. 5D illustrates an alternative format for transmitting relativelysmall numbers of frames of data bits which do not require multiple FRAMEGROUPS as described above. One difference between the format of FIG. 5Dand the preceding format of FIGS. 5A-C is that the synchronizationmarker S" and FRAME GROUP # have been deleted. Reconstruction ispossible, as described below in FIG. 23, where all of the erroneousuncorrectable bits are determined to be totally in the field of theerror correction code bits. The shortness of the field of the data bitsmakes resynchronization unnecessary which permits the elimination of thesynchronization marker S". Since there is only one FRAME GROUP with allthe data and the command CB being in the ID FRAME GROUP, the addressinformation supplied by the FRAME GROUP # is surplus. The bits which arenot contained in the error correction code bit field are referred to asother bits. The EOF character is positioned where the FRAME GROUP # wasformerly positioned. The number of frames in the ID FRAME GROUP may beincreased or decreased with four frames being only one possible example.The same processing circuitry used to encode the format of FIGS. 5A-C isused to process and encode the format of FIG. 5D.

The subcarrier may be either analog or digital. The modulated analogsubcarrier may be a sinusoidal waveform as illustrated in FIG. 6A andthe modulated digital subcarrier may be a squarewave as illustrated inFIG. 6B. Moreover, the number of bits of data which may be modulated oneach cycle of the subcarrier may be varied from the four bits per cycleof FIG. 6A and four bits per half of cycle of FIG. 6B. The high speedintegration capability of digital signal processors used with thepresent invention consequent from their high clock speed and Harvardarchitecture permits multiples of the number of bits encoded on eachcycle illustrated in FIG. 6B and especially the sinusoidal subcarrier ofFIG. 6A to be achieved with the invention.

In FIG. 6A the sinusoidal subcarrier is modulated at four differentphases (discrete angular positions) of a 360° cycle to encode a one or azero value of the individual bits of the FRAME GROUPS of FIGS. 5A-5C,FIG. 5D or modifications thereof on the sinusoidal subcarrier. Asillustrated, the modulation is diphase quadrature modulation (1 or 0modulated at 45°, 135°, 225° and 315°). FIG. 8 discussed below furtherillustrates a constellation representing the encoding of either a one orzero at each of these four discrete angular phases.

In FIG. 6B a squarewave subcarrier is pulse width modulated with a firsthalf of the squarewave subcarrier cycle encoding four bits of the bitsof the FRAME GROUPS of FIGS. 5A-C, FIG. 5D or modifications thereof.FIG. 9, discussed below, illustrates the possible numerical valuesrepresentative of bit groups which may be encoded with squarewavemodulation as illustrated in FIG. 6B. As illustrated, the pulse widthmodulation has sixteen possible widths encoding a four bit group whichpreferably are proportionate, i.e. a value of one is one sixteenth thewidth of a value of sixteen which facilitates high speed integration bythe at least one digital signal processor of the receiving circuitry.

The present invention is fully compatible with analog and digitaltransmitters of the type commonly used for one-way message transmission(paging) throughout the world and with analog and digital transmittingcircuitry of the type used for two-way wireless transmission throughoutthe world. With the invention, the carrier is modulated with asubcarrier having individual cycles modulated with the serialinformation, as illustrated in FIGS. 6A, 6B and FIGS. 8 and 9 asdiscussed below. Furthermore with the invention, the speed oftransmission is higher than the prior art which approaches ten or moretimes the speed of the transmission of the POCSAG protocol with a lowererror rate than POCSAG and the modified ERMES protocols, and can utilizeless radiated power than that of the POCSAG (e.g. 1/4) and modifiedERMES protocols permitting use of fewer transmitters. Reduction in thenumber of transmitters achieves substantial savings in building out thetransmitting infrastructure and further permits frequencies allocated toexisting IMTS transmitters to be used without modification for two-waywireless transmission.

The encoding format of the protocol of the present invention in eitherone-way or two-way wireless systems differs depending upon whether thetransmitting circuitry is operating in analog mode or digital mode. Whenthe transmitting circuitry is operating in analog mode, the encoder,which preferably uses at least one digital signal processor to modulatesinusoidal cycles of a subcarrier, as illustrated in FIGS. 6A and 8produces the serial information with encoded bits in FRAME GROUPS, asillustrated in FIGS. 5A-C, FIG. 5D or modifications thereof, which istransmitted by modulating the carrier. In the analog mode the encoder ofthe transmitting circuitry modulates cycles of the subcarrier withmultiple phase modulation at discrete angular positions of thesubcarrier such as, for example, as discussed above in conjunction withFIG. 6A so that a plurality of quadrants of cycles of the subcarrier aremodulated with at least one bit and preferably a plurality of bitsencoding the FRAME GROUPS illustrated in FIGS. 5A-C, FIG. 5D ormodifications thereof. Diphase quadrature modulation, as discussed abovein conjunction with FIG. 6A and below in FIG. 8, is only exemplary ofthe numerous angular positions that may be utilized to encode the serialinformation comprised of the FRAME GROUPS of FIGS. 5A-C, FIG. 5D ormodifications thereof by modulating quadrants of a cycle of thesubcarrier with one or more bits.

When the transmitting circuitry is operated in a digital mode, digitalor squarewave cycles of the subcarrier are pulse width modulated withthe serial information. The digital encoder of the transmittingcircuitry, which preferably uses at least one digital signal processor,modulates cycles of the subcarrier with pulse width modulation so thathalves of the cycles of a subcarrier are respectively pulse widthmodulated, as discussed above with reference to FIG. 6B and below inFIG. 9. Pulse width modulation may be used to encode a range of numbersrepresenting a plurality of bits (e.g., four in FIGS. 6B and 9) duringthe successive parts or halves of a single cycle of a subcarrier toproduce encoding of the FRAME GROUPS of FIGS. 5A-5C, FIG. 5D ormodifications thereof.

In the event that receiving circuitry is utilized which has thecapability of receiving multiple channels under control of systembroadcast commands as disclosed in the aforementioned patents, theselection of the 900 MS preamble for "local", single frequency receivingcircuitry provides an added benefit to the multi-frequency receiver ortransceiver. As a multi-frequency receiver, such as the one described inthe aforementioned patents, requires an additional 1800 MS preamble tosuccessively scan fourteen channels and successfully take two samples,the receiver does not wake-up to the local 900 MS preamble. Thisprovides an added battery savings for multiple frequency receivers ortransceivers that are capable of travelling when the protocol of thepresent invention is utilized. Any battery savings that can be affordedto multiple-frequency receivers or transceivers is significant.Multiple-frequency receivers or transceivers by design consume morebattery power than single frequency receivers or transceivers. This isdue to the fact that multiple-frequency receiving circuitry must scanand monitor more than one frequency during travelling and roamingoperation between radio transmitting systems. Multiple-frequencyreceivers have experienced scanning rates of operation for three pagingmonths per year (two regionally and one nationally), and therefore,spend approximately 25% of their receiving time in travelling mode ofoperation that can degrade the battery performance life span of thereceiver. Assuming the same low battery drain technologies can beutilized in both single frequency and multiple-frequency receivingcircuitry, any additional battery savings that can be afforded arebeneficial.

The protocol of the present invention provides such battery savings. Bypermitting the S'/ID wake-up length, as described above with referenceto FIGS. 5A or 5D, to wake-up only local single frequency receivers ortransceivers is of significance. In a local radio messaging system, 85%of the receivers will be for local purposes. By design of the shorterlocal preamble, the multiple-frequency receiver or transceiver utilizingthe protocol of the present invention will not wake-up when localmessages are sent. The local receivers or transceivers wake-up uponreceiving the longer multiple-frequency frequency preambles. However,the battery life impact due to the lower number of travelling receiversor transceivers is minimal.

The command field CB of FIGS. 5A and FIG. 5D is for the purpose ofpermitting the receiving circuitry to be programmed to operate indifferent modes of operation. The command field CB may conveyinformation to the receiving circuitry control processor to determinehow the wireless receiving circuitry processes the information fieldwhich follows including actions to be performed by the receivingcircuitry. The command CB may convey to the receiving circuitry whetherthe message information within the INFORMATION field is numeric, sevenbit ASCII, eight bit ASCII, or sixteen bit ASCII (graphics or Chinese)or other information, such as digital words, etc. The command CB canalso convey to the receiving circuitry whether the message is completeand/or is arriving in portions. The command CB permits multiple messagesor a long message to be broken into several shorter messages as needed.This feature may be necessary in systems with co-reside with other typesof messaging terminal equipment and therefore, short duration messagesmay be assigned by the system controller of the transmitter.

The command CB may also indicate to the receiving circuitry of thereceiver or transceiver if the message is to be routed to an externaldevice, as described in the aforementioned patents, as well as performthe diverse other functions disclosed in the above-referenced patents.This permits direct integration of a wireless receiver or transceiverwithin a laptop or personal computer.

FIG. 7 illustrates a block diagram of a one-way system in accordancewith the present invention for wireless transmission by a transmitter124 of information on a radio frequency carrier 106 modulated with themodulated subcarrier of the present invention. The subcarrier, asillustrated in FIGS. 6A and 6B, is modulated with the bits of the FRAMEGROUPS of FIGS. 5A-C, FIG. 5D or modifications thereof. Moreover, asdiscussed below, it should be understood that the invention may beutilized in two-way wireless systems in which a transceiver performs thedual functions of the processor and protocol encoder 110 and thewireless receiver 104. The system includes a signal processing system102 for providing the modulated subcarrier of the present invention asdiscussed above. The transmitters 124 provide wireless atmospherictransmission of the carrier 106 modulated with the subcarrier of thepresent invention, as discussed above, with the transmission ofinformation being subject to atmospheric fading to at least one radiofrequency receiver 104. The signal processing system 102 may be used tomodulate the subcarrier with either the analog or digital modulation ofFIGS. 6A, 6B, 8 and 9 to produce the serial information as discussedabove and below and broadcast by one or more transmitters 124 of eitheran analog or digital type as is in use in the infrastructure of one-wayor two-way radio frequency transmission throughout the world.Information to be transmitted to the receivers 104 is gathered by atelephone communication through the public switched telephone network(PSTN) and transmitted by a telephone connection between the telephoneoffice 108 and a processor and protocol encoder 110.

The processor and protocol encoder 110 is comprised of a processor whichis preferably at least one digital signal processor and associatedmemory 111 which digitally encodes and stores a serial message or datafor transmissions received from the telephone office 108. The storedENCODED SERIAL MESSAGE OR DATA has the encoded format described above inFIGS. 5A-C, FIG. 5D or modifications thereof. The ENCODED SERIAL MESSAGE0R DATA is modulated on cycles of an analog sinusoidal or digitalsubcarrier or other subcarrier by an analog or digital subcarriermodulator (protocol encoder) 113 to produce the serial information whichmodulates the carrier 106. The processor and protocol encoder 110 may bein accordance with FIG. 12 discussed below. The information to betransmitted may be without limitation inputted to the telephone office108 through any one of numerous types of telephone connections 112 whichis indicative of general inputs which may interface with an operatorsuch as from a business office of a paging service or a telephone inputfrom an E-mail network. Input 114 is connected to a personal computer116 of any design which composes messages or data via keyboard or otherperipheral device which are to be broadcast to the wireless receivers104. In the transmission of E-mail messages, the message may be inputtedfrom an E-mail service which is connected to a plurality of computerswhich have identification subscriber numbers of the Email service ordirectly from PC's 116 connected to the telephone office 108 forbroadcast to a laptop personal computer 118 which is connected to thewireless receiver 104 by a serial data port connection 120 of the typetypically available on a laptop PC such as an RS-232 data port. Theinformation which comprises the frames of information of the FRAMEGROUPS of FIGS. 5A-C, FIG. 5D or modifications thereof may be withoutlimitation units of encoded numeric, alphanumeric, graphics informationor any other type of information, such as digital words, etc. ofdiffering bit length. A conventional simulcast controller 122 controls aplurality of transmitters 124 for broadcasting the FM modulated carrier106 which is modulated by the TX1 and TX2 modulators to produce theanalog or digitally modulated carrier 106. The carrier 106 may bewithout limitation any of the narrow depth of modulation carriers usedfor one-way or two-way messaging such as those usable for the 150, 220,450, 800, 900 MHz bands or higher frequencies. Typically, a plurality oftransmitters 124 are disposed around a geographic area within whichreliable broadcast coverage is desired. As is known, the distance whichmay be covered by a simulcast system comprised of a simulcast controller122 and a plurality of transmitters 124 is limited to the line of sightdistance between the transmitters 124 and the receivers 104. In metroareas severe fading occurs because of multipath distortion and furtherman-made sources of noise are typically present which can produceerroneous uncorrectable bits within individual frames or even loss ofsynchronism where multiple frames are faded to cause at least one bit ofclock timing of the receiving circuitry to be lost which results in alost transmission unless resynchronization of the clock timing of thereceiving circuitry processing the group of bits which comprise a framecan be reestablished. Modems 126 must be disposed between the processorand protocol encoder 110 and simulcast system controller 122 and thesimulcast system controller and the plurality of transmitters 124 whenthe carrier is digitally modulated. The modems 126 perform theconventional function of converting the output digital signal from theprocessor and protocol encoder 110 and the simulcast system controller122 into a audio bandwidth sufficient for transmission over narrow bandaudio lines such as telephone lines and back to digital at the far end.When the system utilizes analog transmitters 124, which do not requirethe presence of the modems 126, the processor and protocol encoder 110provides the ENCODED SERIAL MESSAGE OR DATA to be wirelesslytransmitted. The information encoding protocol of the subcarrier for usewith analog transmitters is preferably multiple phase discrete anglemodulation of a subcarrier as illustrated FIG. 6A and in FIG. 8 and theinformation encoding protocol for use with digital transmitters ispreferably the pulse width modulation of a subcarrier, as illustrated inFIG. 6B and in FIG. 9, to produce the serial information having theformat of the FRAME GROUPS of FIGS. 5A-C, FIG. 5D or modificationsthereof.

As is apparent, numerous permutations of modulation of the cycles of thedigital or squarewave subcarrier are possible with the serialtransmission of information in accordance with the invention. Moreover,increasing the number of numeric values or discrete angular phases beingmodulated for a given subcarrier frequency, such as doubling the values,proportionately increases the information throughput transmission rate.Doubling the subcarrier frequency with the same number of bits per cyclebeing modulated also doubles the throughput transmission.

The processor and protocol encoder 110 which comprise the transmittingcircuitry and operation thereof is further described below inconjunction with FIGS. 10 and 12. The receiving circuitry contained inthe receiver 104 is described below in conjunction with FIG. 13.However, it should be understood that the present invention is notlimited to the preferred embodiments of the processor and protocolencoder 110 and receiver 104 described below.

FIG. 10 illustrates a block diagram of the transmitting circuitrycomprising the processor and protocol encoder 110 of FIG. 7. FIG. 10 isidentical to the prior art of FIG. 4 except that a multiple phasediscrete angle of modulation and/or pulse width modulation encoder 100is connected to the digital data bus 58 to permit the encoding of priorart protocols used for one-way and two-way messaging as well as thepracticing of the present invention in encoding the analog or digitalmodulation of the subcarrier as described above with reference to FIGS.6A and 6B and FIGS. 8 and 9. The architecture of the multiple phaseand/or pulse width modulation encoder 100 is described below in detailin FIG. 12. It should be understood that FIG. 10 represents only one ofmany possible embodiments of the transmitting circuitry comprising theprocessor and protocol encoder 110 which may be used in practicing theinvention.

In an analog mode of transmission, an example of the modulation of thebits comprising the serial information in the form of the FRAME GROUPSof FIGS. 5A-C, FIG. 5D or modifications thereof may be visualized foreach cycle of the subcarrier as a repeat of the constellation of FIG. 8with four discrete angles of modulation to encode zeros 140 and ones142. If each cycle of the subcarrier is modulated by the encoded serialinformation as illustrated in FIG. 6A, and also as described in detailbelow when, for example, eight bit ASCII characters are separated intofour bit nibbles, the serial information has bits of each of two fourbit nibbles encoding one character modulated at the 45°, 135°, 225° and315° positions in quadrants of successive cycles of the subcarrier.

The digital mode of transmission of the serial information stream may bevisualized with respect to FIGS. 6B and 9. One or more sequential halvesor parts of the digital or squarewave subcarrier are modulated with theencoded serial information over a sequence of cycles of the subcarrier.Each half of a subcarrier cycle encodes a four bit nibble of for examplean eight bit ASCII character encoded on a full cycle. However, asdescribed above, a greater range of numbers may be encoded in each halfof the squarewave subcarrier. The receiving circuitry comprising atleast one processor, which is preferably a digital signal processor, hasthe integration capability, as described below in conjunction with FIG.15, which facilitates detection of a greater range of differentmodulation widths per cycle of subcarrier.

The error correction bits that are embedded in each of the frames of theserial information provide the receiving circuitry with the capabilityto correct minor transmission errors in the event of short natural orman-made interferences that occur during the transmission of the FRAMEGROUPS of FIGS. 5A-C, FIG. 5D or modifications thereof. As has beendescribed above, each frame may be comprised of forty five bits ofinformation and error correction code to be received by the receivingcircuitry. The bits of error correction information may be withoutlimitation in the form of a 45/24 BCH error correction code such thateach frame is comprised of twenty four bits of information or dataoptionally comprised of three eight bit data units which may be extendedASCII characters, when the information being transmitted is characterbased to which is added twenty one bits of error correction code.However, when longer natural or man-made interferences occur that have aduration of several milliseconds or more, the receiving circuitry upondetecting the predetermined bit error such as a three bit or largererror, which results from a fade that may cause loss of receivingcircuitry clock synchronism and results in erroneous uncorrectable biterrors in one or more frames of the FRAME GROUPS of FIGS. 5A-C, FIG. 5Dor modifications thereof processes the serial information of individualframes containing one or more erroneous uncorrectable bits to attempt torecover faded portions of data units which otherwise would be lost. Therecovery of information within a frame which contains bit errorsexceeding the bit error correction capacity of the error correction codetherein and the resynchronizing of the clock of the receiving circuitryis described below in detail. However, it should be understood that theaforementioned improvements of the present invention are achieved withthe use of the high speed processing capability of digital signalprocessor in the receiving circuitry without additional bit overhead inthe frames of information which, when modulated on the subcarrier withanalog or digital subcarriers, as described above, provides asubstantial increase in data throughput which may be an order ofmagnitude higher than the POCSAG protocol at substantially lower errorrates with lower radiated power being required than used with the POCSAGand modified ERMES protocols.

FIG. 11 illustrates a representative example of the various entries thatare needed to optimize the encoding protocol efficiency. Entry one ofFIG. 11 is a system-wide entry that indicates to the transmittingcircuitry whether the data units in the form of characters, words, data,etc. should be sent to the radio transmitter, transceiver or basestation system in a digital or an analog format. Entry two of FIG. 11indicates to the transmitting circuitry what the maximum rate oftransmission that the radio transmitter, transceiver or base station iscapable of accommodating. The maximum rate of transmission is alimitation that is solely dependent upon the radio transmitter,transceiver or base station and the frequency of the subcarrier.Transmission may be sent at any rate slower than the maximum rate toaccommodate the various generations of receivers, transceivers or basestations that may have slower receiving circuitry. Entry three of FIG.11 is an entry that is common on wireless radio transmitting systemswhich is the finite period of time required for the encoding controlleror a simulcast system controller 122 in a one-way wireless system or ina two-way wireless system illustrated in FIG. 20 to send commands to theradio transmitters or base stations to turn on. This time delay can varydramatically depending upon the system configuration. It may be as shortas a few hundred milliseconds and as long as several seconds whennumerous radio links are utilized to convey the transmitter or basestation turn on information to the radio base station. This programmableentry allows system technicians to program the period of time or pausebetween the time the encoder sends the key transmitter or base stationsignal and begins the actual transmission of the protocol. Entry four ofFIG. 11 indicates to the encoding controller the configuration and/orpresence of additional equipments that may be utilizing the same radiotransmitting system. A multitude of different types of transmittercontrollers and radio message encoders or paging terminals are presentin the one-way and two-way wireless industry. There are very fewindustry standards as to the type of control between the two co-residingcontrollers for the radio channel. Therefore, this two character,alphanumeric entry permits a wide variation of timing as well as logiclevel interfaces to be utilized to permit co-existing with other pagingand messaging equipments as well as two-way wireless equipment. Entryfive of FIG. 11 indicates to the encoder the duration that it will haveaccess to the channel. In many systems it is required or desired tolimit the amount of air-time utilized by either of the two controllers.This is to permit an opportunity for each to distribute the messagesthey have to the radio transmitting system of a one-way or two-waywireless system in a timely fashion. Entry five also permits a level ofsafety for the radio transmitter of a one-way or two-way wirelesssystem. It assures that in the event of a malfunction, the encoder ofthe transmitting circuitry will relinquish control of the transmittingsystem back to the co-resident controller within a fixed period of time.

The processing of the serial information stream by the transmittingcircuitry may use the following steps to prepare the message fortransmission with reference to FIGS. 10 and 12. They are:

1. The resident processor U1 illustrated in FIG. 12, of the processorand encoder and processor module 100 of FIG. 10 receives the wirelessreceiver's or transceiver's ID, command CB, information or data to betransmitted, and end-of-file marker EOF from the main central processingunit such as the CPU 30. The information to be transmitted, as statedabove, may be of diverse form such as data but for purposes of thisexample is assumed to be an alphanumeric message.

2. The resident processor U1 of the encoder and processor module 100makes the conversion of the alpha numeric including the addition of therequisite number of bits of error correction code to each frame messageinto a format, as illustrated in FIGS. 5A-D, FIG. 5C, FIG. 5D ormodifications thereof. Two digits of the receiving circuitry'sidentification code are added to the S'/ID portion of the message asexplained above in conjunction with FIGS. 5A and D. This permits anoptimization of the wireless receiver's or transceiver's batteryefficiency as previously described.

3. The resident processor U1 of the encoder and processor module 100causes storage of the encoded serial message encoded in the form of theID, DATA, and SHORTENED EOF FRAME GROUPS, as illustrated in FIGS. 5A-D,FIG. 5C, FIG. 5D or modifications thereof. The memory processing andstorage may be performed in the RAM U17 and U43 of FIG. 12.

4. The resident processor U1 of the encoder and processor module 100fetches the serial information comprised of the ID, DATA and SHORTENEDEOF FRAME GROUPS of FIGS. 5A-C, FIG. 5D or modifications thereof fromthe RAM memory U17 and/or U43 of FIG. 12 including the synchronizationmarkers S" and FRAME GROUP #'s and BCH or other error correction code.The synchronization markers S" are added to permit the receivingcircuitry processor U7' illustrated in FIG. 13 to recover the data bitsin each frame of the frame groups and/or maintain synchronization whenfaded information is in excess of the bit error correction capacity ofthe frames of the frame groups information stream as discussed belowwith reference to FIGS. 23-25, 26A-C and 27. The formatted message inaccordance with FIGS. 5A-D, FIG. 5C, FIG. 5D or modifications thereof isstored in the transmission buffer memory U17 or U43 of FIG. 12.

5. The resident processor U1 of the encoder and processor module 100then waits for the availability of the analog or digital radiotransmitter. Upon gaining access to the radio transmitter of a one-wayor two-way wireless system, the resident control processor U1 of theencoder module and processor 110 fetches the stored message formatted inaccordance with FIGS. 5A-C or FIG. 5D to be transmitted from thetransmission buffer memory and forwards the formatted message to theencoder and processor 100 for modulation on the cycles of the subcarrierin either the analog (e.g., FIGS. 6A and 8) or digital (FIGS. 6B and 9)format for radio transmission as described above.

If the preceding cycle of the subcarrier contains all binary ones, thenext cycle of the subcarrier is inverted to contain all zeros for thepurpose of receiving circuitry synchronization. This is to insure that acycle transition occurs during the end of the modulation of a half of acycle of the subcarrier to insure that the digital signal processor U3',of FIG. 13 of the receiving circuitry as described below maintainssynchronization during the synchronization window. If a transition doesnot occur during the synchronization window, the digital signalprocessor U3' maintains the precalculated sync and waits for thesynchronization window to resynchronize the receiving circuitry to theincoming data stream. The stability of the internal receiving circuitryoscillator is such that approximately 600 consecutive synchronizationtransitions may be missing without causing a total loss of the receivedserial information.

The encoder and processor module 100 receives the following informationfrom the main processor 30:

1. The one or more messages or data to be transmitted having the samepreamble.

2. The ID code of the receiving circuitry of receiver(s) ortransceiver(s) to receive the wireless transmission.

3. A command CB from the main CPU 30 subscriber file (by default) or acommand CB that has been received by the message originator.

4. The message text or data which may be four bit groups (nibbles)encoding numeric base 10 information, seven bit, eight bit ASCII orsixteen bit graphics or other information.

5. The speed of data transmission.

6. The mode of data transmission (analog or digital).

7. The special EOF command of the SHORTENED EOF

FRAME GROUP of FIG. 5C and FIG. 5D.

The resident control processor U1 of FIG. 12 in the encoder andprocessor module 100 adds the following information to the messagestream during the encoding process:

1. The 45/24 BCH error correction code or other error correction codechosen for the one-way or two-way wireless application.

2. The synchronization marker S" and FRAME GROUP # as illustrated inFIGS. 5A-B.

3. The EOF termination command as illustrated in FIGS. 5C and D.

FIG. 12 illustrates a preferred embodiment of the transmitting circuitrycomprising the encoder and processor module 100 in the form of a blockdiagram containing the necessary electronics to interface the digitalhighways from the main control CPU 30 and process the information fortransmission to an analog and/or digital one-way radio system such asthat of FIG. 7 or a two-way radio system such as that of FIG. 20described below. The encoder and processor module 100 contains theinterface electronics necessary to meet the many diverse interfacerequirements that are present in the one-way and two-way radiotransmitter industry. Data arrives from the central processor 30 via theeight bit DATA BUS to buffer circuits U46 and U53. The message data orinformation is temporarily stored in a "first in, first out" memory thatprovides a form of elastic storage for the board resident processor U1.When the board resident processor U1 is alerted that information existsin the FIFO memory, the data is transferred and stored via the dataaddress control bus to RAM memories U17 and U43 for processing. Uponsystem initialization, the board resident processor U1 is alerted as tothe default transmission speed to which messages will be sent, and alsoa default mode of data transmission (analog or digital). The boardresident processor U1 has a stored program that controls the encodingprocess as described above that is contained in EPROM U34. Theinformation and ID which are received as previously described from thecontrol processor 30, are then converted to the encoded serial format ofthe FRAME GROUPS containing frames with embedded error correction codeas described above in conjunction with FIGS. 5A-C, FIG. 5D ormodifications thereof. The control processor U1 attempts to gain accessto the radio transmitter of the one-way or two-way wireless system suchas that illustrated in FIG. 7 or FIG. 20 described below. Depending uponthe interface configuration, the resident control processor U1 searchesfor a status control signal from either the radio base station or theexternal simulcast controller 122 or two-way wireless controller ornetwork switch 602 via the clear to send line or station busy signal asit is commonly referred to in the industry. Upon determination that theradio transmitter 124 of a one-way wireless system or a transmitter of atwo-way wireless system is not busy, the resident control processor U1keys the radio transmitter by a digital logic signal that is sent by acontrol latch U49.

It may be necessary to send several signals to the one-way or two-wayradio transmitter from the control latch U49 depending upon the systemconfiguration. A second logic signal called "mode" may also be sent toindicate to the radio transmitter or the simulcast controller 122 of aone-way wireless system or transmitter or network switch of a two-waywireless system if the desired message is to be sent in an analogconfiguration or in a digital FSK or PWM configuration. In many systemconfigurations transmitter zones are also utilized and one or more ofthe zone outputs may be enabled to select the required transmitting areato transmit the message.

Upon completion of the turn on sequence of the radio transmitter of theone-way or two-way wireless system, the board control processor U1 sendsthe formatted data and a mode command to the digital signal processorU47. U47 is a board resident co-processor which preferably is a digitalsignal processor that modulates the subcarrier with binary informationusing the multiple phase discrete angle or PWM modulation, as describedabove, or other analog or digital protocols using the system parametersthat have been sent to the board resident processor U1 by the mainprocessor 30. The encoding format, as described above and errorcorrection routines, such as the 45/24 BCH error correction routine in aone-way wireless application or other error correction routine in atwo-way wireless application, that needs to be added to the serialinformation resides in a resident stored program memory U50. In theexample given above, four bit nibbles of the message are sent insequential order by the board resident processor U1 to the digitalsignal processor U47 for processing. The message is temporarily storedin the 2K RAM buffer U46 and the digital signal processor forwards theinformation to either the digital shift register U13 to produce thedigital format of FIGS. 6B and 9 for transmission by a digitaltransmitter, or to the CODEC U48 to produce the analog format of FIGS.6A and 8 for transmission by an analog transmitter.

The digital signal processor U47 also has access to and is capable ofgenerating modem tones by accessing the board resident modem U24. Theoutput of the modem is then connected to the analog ports via dataswitches for transmission to the analog radio transmitting system.

With the system configuration information that resides in the controlprogram of the main processor 30, numerous interface configurations maybe obtained by the encoder and processor 100 to a one-way radiotransmitting system such as that of FIG. 7 or a two-way wireless systemsuch as that of FIG. 20 described below. The encoder and processor 100also has the ability to receive data from other modules that may existin the encoding mechanism. That information arrives from the PCM DATAbus and can be sent via an analog switch directly to the CODEC U48 fortransmission to the analog radio transmitting system. This connection tothe external digital PCM highways can permit voice messaging or otheranalog paging tones to be sent from the synthesizer module. As manymessaging systems have multiple formats that co-exist on the same radiotransmitter, two tone signaling, 5/6 tone signaling, DTMF signaling,POCSAG and Golay protocol formats and two-way formats may also betransmitted by the processor and encoder 100 via the external PCM ports.

The digital signal processor U47 may also send digital data directlyback to the PCM DATA bus to another module. In the event that a purelyanalog system with multiple analog radio channels is utilized, thedigital data of the digital signal processor U47 may be sent to a dualchannel board module (not illustrated). If frequency agile receivers ortransceivers are utilized, as described in the above-referenced patents,this is the preferred mode of interface to the multiple radiotransmitters. One encoder module can be utilized to gain access tonumerous radio channels without the need for additional encoder modules.

Upon completion of the transmission of the message, the digital signalprocessor U47 alerts the board resident control processor U1 that themessage is complete. The board resident control processor U1 thensignals the main processor 30, via control signals and the eight bitDATA bus, that it is ready for transmission of new messages.

When the message is ready for transmission, the one-way systemcontroller 122 of FIG. 7 or network switch 602 of FIG. 20 requestsaccess to the radio transmitter facility and begins the transmissionprocess. Often times the one-way radio controller mechanism 122 ortwo-way network switch 602 must co-reside and/or exist with other radiocontrol equipments and share the same radio transmission facility. Suchco-existence is commonplace in the industry and is accomplished by crossconnecting the equivalent of clear to send and ready to send controlsignals with each other to permit the two system controllers to co-existwithout conflict or collision. This co-existence permits messagingfacilities to utilize many other types of radio equipments that they maycurrently have. The control mechanism and protocol can co-reside andco-exist with the hundreds of various signaling protocols that arecurrently being utilized in the industry today.

When the transmitter 124 is available for use by the system controller122 in a one-way wireless system or the transmitter for use by thenetwork switch 602 or other controller in a two-way system is available,the transmission of the serial transmission in the form of FRAME GROUPSof FIGS. 5A-C, FIG. 5D or modifications thereof begins. The encodermodule microprocessor U1 fetches the stored serial information asdescribed with reference to FIGS. 5A-C, FIG. 5D or modifications thereoffrom the random access memory modulates the subcarrier and forwards themodulated subcarrier to the modulator of the transmitter which modulatesthe radio frequency carrier 106 of the one-way system of FIG. 7 ortwo-way system of FIG. 20.

The SYNC signal S' is sent at the subcarrier rate that has beenpreviously programmed into the encoding controller by entry two of FIG.11. The SYNC signal S' purpose is to alert the digital signal processorU3' of the receiving circuitry in FIG. 13 that information isforthcoming, and also serves as a battery saving technique to wake-uponly the receivers 104 or transceivers 700 assigned to that particularprefix or synchronization group as described above. This has a neteffect of providing a tremendous battery savings, as only a portion ofthe receivers or transceivers in a system wake-up at this point andconsume battery current. All receivers or transceivers that do not seethe SYNC signal S' pattern that corresponds to its synchronization codeand two digits of the ID code of the ID FRAME GROUP of FIGS. 5A and Dremain in a low current sampling mode.

The receivers 104 or transceivers 700 that have now received thesynchronization code S' are now awaiting the balance of the serialtransmission of the DATA FRAME GROUPS, and the SHORTENED EOF FRAME GROUPof FIGS. 5A-C or the remainder of the information of FIG. 5D.

The ID code has fourteen digits as described above with two of thedigits being placed in the previously described first frame of the IDFRAME GROUP, to maximize the battery efficiency of the wirelessreceivers or transceivers. The first two digits of the ID code arefollowed by a COMMAND code CB. The command code CB, as explained above,alerts the receiving circuitry as to the nature or type of informationthat is about to follow. It can request that the receiver or transceiverstore the information internally, or direct it to an external port to aperipheral device, such as a laptop PC 118, and also convey informationto the receiver as to the nature of the type of message and performother functions including the commanded functions described in theabove-referenced patents. For example, the command code CB may alert thereceiving circuitry that the information to follow is seven-bit ASCIIinformation, eight-bit ASCII information or sixteen-bit information (inthe event of graphics or Chinese characters or other information),digital words, control an alarm function, etc.

The serial information encoded in one or more sequentially addressedDATA FRAME GROUP(S), as described above in conjunction with FIG. 5B, isterminated with the SHORTENED EOF FRAME GROUP as described above inconjunction with FIG. 5C containing the EOF or end of transmission wordor EOF end of transmission of FIG. 5D which are sent to indicate to thereceiver 104 or transceiver 700 the termination or completion of theserial message text.

The transmitting circuitry of the present invention interfaces withradio transmitters of either one- or two-way wireless systems in eithera digital or analog subcarrier modulation format. The protocol may besent via analog or digital radio transmitters. This hybrid transmissionprotocol is beneficial due to the fact that there exists, bothdomestically and globally, an almost even distribution of both analogand digital radio transmitters in one-way and two-way wireless systems.Typically, large metro city radio transmitting systems in one andtwo-way wireless systems can accommodate both analog and digitalsignaling protocols. Smaller and rural paging systems may typically beexclusively analog in nature. Private paging systems such asmunicipalities, factories, and hospitals typically utilize analog radiotransmitters because analog radio transmitters are lower in cost. Whenthe digital format is utilized, the characteristic clear to send, readyto send and digital data output of the protocol controller U1 of FIG. 12is connected typically to a modem.

Currently, the one-way and two-way wireless industry uses 1200 baudasynchronous modems quite extensively and the design of equipment inaccordance with the invention emphasizes immediate compatibility withthe current radio messaging infrastructure. When connected to a digitalradio base station in a one-way or two-way wireless system, the encoderand processor 100 produces the pulse width modulation of the subcarrieras illustrated in FIGS. 6B and 9, to encode a selectable number within arange of numbers representing a groups of bit during each half cycle ofthe subcarrier which encodes the serial information in the format ofFIGS. 5A-C, FIG. 5D or modifications thereof. Various widths of thesubcarrier encode different numbers which cause positive or negativedeviation of the FM radio transmitter. By varying the width of each partof the subcarrier, pulse width modulated encoded units of information,such as four bit nibbles, are modulated upon the subcarrier.

There is movement in the industry underway to increase the subcarrierfrequency of the radio transmitters from 1200 Hz. to 2400 Hz. andbeyond. It is for this reason that the variable data rate has beendesigned into the format. As faster modulation rates are obtained by theradio transmitter manufacturers in one-way and two-way wireless systems,the protocol of the invention can be used to increase the datathroughput rate.

The encoding controller U1 of FIG. 12 also has the ability to bedirectly interfaced to an analog transmitting system in a one-way ortwo-way wireless system. The encoding controller U1 contains a modemcapable of encoding in accordance with the example of FIG. 6A. Theencoding controller U1 is directly connected via a radio link or wirepairs to the radio transmitter 124 in a one-way wireless system or tothe radio transmitter 614 in a two-way wireless system as discussedbelow in conjunction with FIG. 20. When the encoding controller U1 isutilized in an analog fashion, an example of the wave form of the datastream appears as shown in FIGS. 6A and 8. Each of the four phases (45°,135°, 225°, 315°), represents a part of the serial information that maybe modulated to encode a binary zero or one. The binary one 142 is thehigher of the two amplitudes and the binary zero 140 is the lower of thetwo amplitudes of FIG. 8. This permits multiple bits of data to be sentin serial format with their respective significance in the data streambeing encoded at discrete phase angles of the sinusoidal subcarrier. Thechoice of the number of phases located at discrete angular positions ofthe subcarrier which are modulated by the serial information format ofFIGS. 5A-C, FIG. 5D or modifications thereof may be varied in practicingthe invention.

The transmitting methodology of the present invention is both analog anddigital radio transmitting system compatible in one-way and two-waywireless systems and further meets the required telephony bandwidths andthe existing infrastructure radio transmitter requirements to assurecompatibility in the current marketplace.

The net result of the encoding mechanism using the serial format ofFIGS. 5A-C, FIG. 5D or modifications thereof and the high speed analogor digital modulation of the subcarrier of FIGS. 6A, 6B, 8 and 9 permitsrapid implementation of the protocol with minimal capital expenditure topermit the messaging facility to gain entry to more profitablealphanumeric information and E-mail services. The efficiency of theprotocol of the present invention permits a paging facility with asingle frequency transmitting facility or a two-way wireless system thatis currently air time restricted while only accommodating numeric pagingsubscribers to gain additional air time to entertain new services andsubscribers.

The digital signal processor U3' of the receiving circuitry of FIG. 13processes the detected individual modulated cycles of the subcarrier inthe format of FIGS. 6A and 6B to calculate an integral of at least oneselected modulated part of each of the modulated cycles. A selectedmodulated part when pulse width modulation is used is each of the firstand second halves of the squarewave which each contain pulse widthmodulation that may encode any one of a range of numbers representing apart or a data unit as explained above with reference to FIG. 6B and 9.A selected modulated part when multiple phase discrete angularmodulation of a sinusoidal subcarrier encoding bits at spaced apartangular positions is used has been explained above with reference toFIGS. 6A and 8. Each of the calculated integrals is numerically comparedwith a plurality of stored numerical ranges to identify a range whichcontains the numerical value of the integral. Each range represents oneof a plurality of possible numerical values that the selected part mayencode. These stored ranges represent the possible integrated values ofthe subcarrier modulation encoding a bit having one and zero value whenmultiple phase modulation is used as discussed above with reference toFIGS. 6A and 8 or the possible integrated values of the subcarriermodulation encoding a group of bits having the individual numericalvalues within the numerical range of pulse widths as discussed abovewith reference to FIGS. 6B and 9. The numerical comparison is discussedin detail below with reference to FIG. 18. A binary representation ofthe numerical value representative of the identified numerically closestrange in which the calculated integral is found is substituted andstored in memory for each of the at least one selected modulated part ofeach of the cycles. The substitution process is discussed below withreference to FIG. 18. The numerical value encodes at least a part of aninformation unit of the serial information. For example, when the serialinformation is a series of characters and pulse width modulation is usedin accordance with FIGS. 6B and 9, each numerical value represents fourbits which is one-half the information required to encode a fullcharacter with ASCII.

The modulation of the subcarrier in either analog or digital format isconverted by the digital signal processor U3' of the receiving circuitryof FIG. 13 from a time varying signal of FIGS. 6A and B to a series ofnumbers encoded as bits representing part of or a complete data unit(s)which facilitates processing of faded information as discussed below.The series of numbers are stored in the memory U4' as data bits whichrepresent the detected information including error correction code inthe format of FIGS. 5A-C, FIG. 5D or modifications thereof.

The digital processor U3' of FIG. 12 further performs processing ofindividual samples, which are taken to calculate the aforementionedintegrals and to remove the effects of noise causing a sample value tofall outside a normal expected range. Each sample value is compared bythe digital signal processor U3' with a range which representsacceptable sample values. If the comparison yields a determination thata sample is numerically within the acceptable range, the sample is usedin the integration without modification. However, if the sample isnumerically outside the acceptable range, the sample is replaced with anumerical value representing a function which may be an average of oneor more adjacent samples that are stored in memory which may bepreceding and following samples of the sample outside the numericalacceptable range. As a result, the effects of noise in causing anerroneous integration of a selected part of a cycle of the subcarrierare substantially lessened. This process is described below withreference to FIGS. 16A and B and 17A and B.

Most importantly the digital signal processor U3' of FIG. 13 providesthe ability to analyze the detected modulated subcarrier for thepresence of valid information. For example, when a pulse width modulatedor phase modulated waveform is received, the digital signal processorU3' takes numerous samples of the area under the waveform. This permitsthe digital signal processor U3' to determine the value of each multiplebit group or individual bits of information modulated on the subcarrier.The pulse width or duration or a plurality of phases at spaced apartangular positions of the subcarrier encodes each multiple bit group orbit of information that it represents. Due to the high sample rate andprocessing architecture of the digital signal processor U3', hundreds ofsamples can be made of the area under each cycle or part of a cycle asdescribed below with reference to FIGS. 14A, B and 15 to very accuratelydetermine by integration the numeric value of the data that the pulsewidth modulated signal or phase modulated subcarrier encodes. This isespecially important to remove the effects of phase distortion and otherdegradations of the subcarrier which are prevalent in transmitting datawirelessly. By integrating the area under the curve, an extremelyaccurate analysis of the pulse width modulated or phase modulatedwaveform can be made that eliminates distortions that are typical at theleading and trailing edges of a digital waveform. These distortions areaggravated in the wireless environment. Noise spikes that appear on thewaveform are easily negated by an integration of the area under thewaveform. Noise spikes on a waveform that occur during the transitionsof the waveform do not effect the ability of the digital signalprocessor U3' to maintain synchronism of the incoming serialtransmission and do not cause an erroneous determination of the dataencoded with the pulse width modulation or the modulation at spacedapart angular positions of the subcarrier.

The digital signal processor U3' of FIG. 13 looks for the S'/ID wake-upto determine the rate of information transmission as well as if itshould continue the receiving circuitry turn on process if the two IDdigits in the ID FRAME GROUP match that of the receiving circuitry ofthe receiver or transceiver. When the digital signal processor U3' hasdetermined the rate of information transmission and the type of datatransmission, it fetches from the microprocessor U7' stored program codeto maximize the decoding reliability. The digital signal processor U3'has the ability to set or alter the bandwidth of the received data tomask unwanted received components or information. The digital signalprocessor U3' provides the clock recovery by utilizing an energy basedclock recovery technique. This clock recovery technique is considerablymore reliable than utilizing zero crossovers. Zero crossovers typicallycan be severely distorted by multipath unalignment of multiplesimulcasting transmitting systems. The energy based clock recoverytechnique utilizes and detects the midpoint of each cycle of thesubcarrier. It does so by summing the energy, or the area under thecurve or phase (angular position) of the subcarrier as described above.This increases the receiving circuitry's detection sensitivity by makingit immune to distortions that are inherent in simulcast messagingsystems of the wave form as well as the zero crossover transitions. Dueto the high processing speed of the digital signal processor U3', realtime preprocessing of the serial information, including integration andsample processing, as described above, can occur prior to the data beingsent to the control microprocessor U7' for information decoding andrecovery and reconstruction of erroneous information and maintaining ofsynchronization and resynchronization to provide an improved signal tonoise ratio which is calculated to be about three db attributable to theintegration process and another 20% attributable to sample signalprocessing.

The digital signal processor U3' utilizes a modified Harvardarchitecture with multiple pipelining to permit the maximum number ofcalculations and samples to be made of the received information. Due tothe high sample rate of the digital signal processor U3' and itsmultiple pipeline architecture, the digital signal processor can providenumerous real time preprocessing steps to optimize and correct anomaliesin the received waveform.

The digital signal processor U3', as with any other type of informationdecoder, has performance trade-offs. Most fixed hardware designeddecoders have to select between bandwidth and the bit error rate of thedata it receives. The wider the bandwidth, the quicker the decoder cansynchronize and lock on to the incoming carrier. However, when thebandwidth is increased the decoder becomes more susceptible to noise andthe bit error rate of the detector increases. If a narrow bandwidthdecoder design is utilized, the bit error rate is lowered but thecarrier synchronization time is increased substantially. The digitalsignal processor U3' resolves this problem in that during the samplingtime the bandwidth is dynamically programmed by the stored program tohave a wide bandwidth to permit a rapid detection of the receivedcarrier 106 or 616. However, as soon as the carrier is received, thestored program then provides supportive software to narrow the bandwidthto optimize the integrity of the received data. It is this dynamicoperation of the digital signal processor U3' that is under controlmicroprocessor U7' and stored program control that permits the receivingcircuitry to rapidly detect and synchronize to an incoming signal andthen optimize the integrity of the received data by narrowing thebandwidth.

Upon completion of the preprocessing involving integration and samplesignal processing by the digital signal processor U3', the digitalsignal processor forwards the decoded serial binary information from thebuffer RAM U4' to the microprocessor U7' for decoding and recompilationof the received data. The microprocessor U7', under stored programcontrol, fetches the error correction code that is embedded in theserial encoded information for correcting minor bit errors (e.g. two orless) and tests each frame to identify when a frame contains at leastone erroneous uncorrectable error bit exceeding the bit error correctioncapability of the error correction code as described below inconjunction with FIGS. 23-25, 26A-C and 27 The serial data, includingerror correction, code is stored in random access memory U8' for laterprocessing as described below when larger irrecoverable errors (fadedinformation) are detected which require reconstruction alone or afterresynchronization of the clock of the receiving circuitry.

The microprocessor U7' is also responsible for controlling the residentdisplay electronics and control of the external data port fortransmission of the received information to an external peripheraldevice such as the laptop PC 118.

FIG. 13 illustrates a 10-chip set decoder and control of the receivingcircuitry which may be implemented in receiver 104, transceiver 700 orassociated with a base station. The decoding mechanism, can be connectedto a number of different receiving circuitry configurations at thediscriminator audio entry point inputted from the audio detector 190.Various receiving circuitry configurations can be a single frequencycrystal controlled single or dual conversion type of receiver. Amulti-frequency or scanning type of receiving circuitry utilizing aprogrammable phase lock loop for multi-channel reception may be used, orthe decoder may be connected to a mobile or portable two-way transceiverthat is either single or multi-frequency using multi-crystal orprogrammable synthesizer technologies.

The decoder may be further integrated by LSI technologies to a 3-chipset. The integrated circuits U2', U3', U4', U5', and U6A',B' arecurrently available in a single digital signal processor. The controlCPU U7', RAM memory U8', 8K ROM memory U9', address control U6F', andI/O port U6E' are currently available in a single LSI microcircuit. Theremaining electronics, consisting of the receiving circuitry controlU6C' and clock oscillator U6D' are integrated into a PAL logic arraythat may be manufactured by National Semiconductor or Texas Instrumentsor other sources.

The operation of the decoder is as follows:

The low pass filter U1' consists of a switched capacitor filter thatlimits the frequency response of the discriminator audio to the 300.3000Hz audio bandwidth. The low pass filter is a fourth order filter thatprevents high frequency noise components from entering the eight bitflash analog to digital converter U2'. The audio detector 190 representsthe audio output from any type of a one-way receiver, such as that inthe aforementioned patents, or two-way transreceiver.

An eight bit flash analog to digital converter U2' is connected to thedigital signal processor U3' via an eight bit DATA BUS 1. Clock signalsare provided by a portion of U6D' that takes a master crystal oscillatorand provides the necessary clock pulses for the processors and the A/Dconverter. Input/output control of data from the flash A/D converter isaccomplished by the A/D control portion U6A'. The clock of the receivingcircuitry is resynchronized by detection of the synchronization markerS" by using conventional techniques for shifting stored bits in memoryor registers to locate the stored synchronization marker S". The eightbit flash A/D converter samples the incoming audio waveform at highfrequency sufficient to take at least hundreds of samples per modulatedphase as illustrated in FIG. 6A or squarewave as illustrated in FIG. 6B.The higher the sample rate, the more accurate the integration is. TheA/D converter converts those samples to eight bit binary words that aresent to the digital signal processor U3' via the eight bit data bus.Timing control is provided by the A/D control U6A' and permits data toexit U2' only when the digital signal processor U3' addresses U2' whendata is present.

The digital signal processor U3' simultaneously reads data from theflash A/D converter U2', processes and analyzes the data, and then sendsthe decoded data via DATA BUS 1 to the control CPU U7'. Decoded andanalyzed data is forwarded to the control CPU U7' between readings ofthe eight bit flash A/D converter.

The digital signal processor U3' may be manufactured by TexasInstruments and is in one of three generations of TMS320XX seriesprocessors. Texas Instruments manufactures low, voltage, low currentprocessors that are applicable to battery operated receiving circuitry.

The digital signal processor U3' is connected to a 2K random accessmemory U4' and a 4K EEROM memory U5'. A second data bus DATA BUS 2 isutilized to permit data to be read by the digital signal processor U3'from and to the RAM memory and from the EEROM memory which contains thestored program. The digital signal processor U3' controls the selectionof reading and writing to RAM memory U4' and reading from EEROM memoryU5' by the address control U6' portion of a custom gate array U6B'.

The digital signal processor U3' is responsible for initiallysynchronizing the receiving circuitry to the incoming serial informationby using the sync address S' of the ID FRAME GROUP of FIG. 5A andresynchronizing the receiving circuitry to the incoming serialinformation by using the synchronization markers S" of theaforementioned ID and DATA FRAME GROUPS of FIGS. 5A and B and providingwaveform analysis for the decoding of the pulse width modulated digitalserial information or the multiple phase serial analog information asdescribed above. Upon completion of the decoding of the received binarydata stream, the digital signal processor U3' forwards the decoded datavia DATA BUS 2 to the control CPU U7'.

The 2K RAM memory U4' serves as a scratch pad memory for the digitalsignal processor U3'. Intermediate calculations and reconstructedreceived data are temporarily stored and buffered in RAM memory U4'. The2K RAM memory also temporarily stores intermediate calculations andinstructions as needed on occasion by the digital signal processor U3'.The 2K RAM memory has a DATA BUS 2 utilized to communicate to and fromthe digital signal processor U3'. This permits the digital signalprocessor U3' to access and store data in the 2K RAM memorysimultaneously while utilizing DATA BUS 1 to receive information fromthe eight bit flash A/D converter or sending information to the controlCPU U7'. It is this architecture that is commonly referred to a modifiedHarvard architecture where the digital signal processor U3' is capableof simultaneously communicating on two separate data buses.

The EEROM memory U5' contains the stored program for the digital signalprocessor U3'. It contains resident softwares that permit the digitalsignal processor U3' to decode both the analog multiple phase and pulsewidth modulation digital subcarrier waveforms respectively of FIGS. 6Aand 6B and the integration processing as described below to convert thedetected subcarrier to binary data and further to eliminate noisetransients as described below. The EEROM memory U5' also contains thesupportive digital signal processor software to permit synchronization,resynchronization of the receiving circuitry, analysis of the receivedwaveform data, storage and transfer of the received data to the controlprocessor U7', and bandwidth control of the received data when thereceiver becomes synchronized to the data stream.

U6' is a custom gate array that provides numerous encoding and decodingfunctions for the multiple phase and pulse width modulation decoder.U6A' provides address and control interfacing between the digital signalprocessor U3' and the eight bit flash A/D converter U2'. It is thefunctional equivalent of an active low address enable IC similar to the74HC138, and also the functional equivalent of the 74HC251 inputmultiplexer that can sense when the A/D converter has data to be read bythe DSP. U6B' provides address control of the 2K RAM memory U4' and the4K EEROM memory U5'. Accessing of data to and from these memories iscontrolled by the digital signal processor U3' via U6B. U6B' is thefunctional equivalent of a 74HC138 3-8 decoder with some additionalgating electronics for read/write control to and from the 2K RAM memoryU4'. U6C' is the receiving circuitry control portion of the custom gatearray. It provides interfacing from the control processor U7' via DATABUS 1 and a control signal from U6F'. The receiving circuitry control ICconsists of the functional equivalent of control latches such as the74HC259 for receiver power. U6C' provides the functional equivalent of atri-state buffer (one section of an HC244) for serial transmission ofdata to the PLL control circuit. U6C' also provides the functionalequivalent of a 74HC251 to sense receiving circuitry carrier detectionand the PLL synthesizer lock conditions. U6C' also provides thefunctional equivalent of a 74HC244 (single section) to provide a serialdata stream to the antenna tuning processor when a multi-frequencyreceiving circuitry is utilized. U6D' provides the necessary clocks forthe control CPU U7', the digital signal processor U3', and the eight bitflash A/D converter U2'. A 25 MHz or higher frequency crystal may beutilized for the decoding circuit. The oscillator section consists ofthe functional equivalent of two 74C04's that are connected in parallelwith the crystal and provide the necessary inversion for the oscillatorand buffering. The balance of U6D' are respective dividers that dividethe clock frequency to the lower 8 MHz required by the A/D converter U2'and 4 MHz required by the control CPU U7'. The clock frequency isbuffered and directly sent to the digital signal processor U3'. The U6E'portion of the custom gate array provides the necessary I/O portbuffering for the external serial port and the control processor U7'data bus of the multiple phase and PWM decoder circuit. Tri-state inputand output buffers and level conversion is provided so that the serialport which operates in a RS-232 configuration can send and receive datato an external device as described above. The I/O port buffers are thefunctional equivalent of a 74HC245 bi-directional tri-state buffer andcontrol latch to encode DSR and RTS data signals (HC259), and a 74HC251eight to one MUX to decode the CTS and DSR received signals from theperipheral device. The buffering and level conversion is accomplished bythe functional equivalent of a 74188 or 74189 RS-232 to TTL levelconverter.

The U6F' portion of the custom gate array is the functional equivalentto an address control decoder that permits the control processor U7' toaddress select the 64K RAM U8', the 8K ROM U9', the I/O port buffers andlatches U6E', the receiving circuitry control portion of U6C', and theliquid crystal display U10'. It is the functional equivalent of a74HC138 3-8 decoder.

The control processor U7' is responsible for all of the controlfunctions of the decoder of the receiving circuitry. It controls allreceiving circuitry control functions, including the turning on and offof the power to the receiving circuitry electronics, digital signalprocessor electronics, and the serial I/O port electronics. The messagesreceived are stored by the control processor U7' in the 64K RAM memoryU8' or are forwarded to the serial port for external use. The controlprocessor U7' is also responsible for sending stored messages from the64K RAM memory U8' to the resident liquid crystal display U10 fordisplay and reading purposes by the user. Control processor U7' alsoresponds to push button requests initiated by the user and/or datarequests initiated by the serial port as necessary.

The 64K Random Access Memory U8' is utilized by the control processorU7' for message storage and retention. A portion of the memory isutilized as working buffer memory and storage of control variables forthe operating program. The 64K RAM is enabled by U6F', the addresscontrol register. Data is transferred to and from the 64K RAM via theeight bit data bus 1.

The 8K Read Only Memory U9' stores the resident software for thereceiving circuitry. It contains all of the operating softwares andsubroutines to permit the control processor U7' to operate the receivingcircuitry. Message decoding routines, error correction routines, andmessage replacement routines are contained in the operating software.The operating software also contains the control and timing electronicsfor the control processor U7' to control the various portions of thereceiving circuitry via U6C'. Service routines to transfer receivedstored messages are also contained in the 8K ROM and via the controlprocessor U7' may be transferred to the liquid crystal display U10,erased, or transferred to the serial port U6E' for external use. A blockdiagram of the receiving circuitry decoding/control processes that arecontained in the 8K ROM are described below with reference to FIGS. 19Aand B. The control flowchart shows the general service routines that areutilized to permit the decoder to turn on the receiving circuitry,sample the channel for presence of carrier and data, and respectivelylook for the receiver or transceiver receiving circuitry correspondingID code and message or data.

The receiving circuitry utilizes a single line dot matrix liquid crystaldisplay. When the receiving circuitry senses a button press via the I/Oport buffer U6E', the control processor U7' in turn responds andforwards messages to the liquid crystal display for display purposes.Alternatively, multi-line liquid crystal displays may be used to permita greater amount of text to be displayed simultaneously.

The integration of an analog subcarrier modulated, as illustrated inFIGS. 6A and 8, is explained in detail as follows. FIGS. 14A and Billustrate the received diphase quadrature modulated subcarrier asreceived from a discriminator of the receiving circuitry in a receiver,transceiver or associated with a base station. The data, as illustratedin FIG. 14A, is encoded at the 45° and 135° phases with the 225° and315° phases having been omitted from the illustration. Regardless of thenumber of spaced apart angular positions of the subcarrier which aremodulated, the determination of whether a one or a zero is encoded inthe modulation involves the discrimination of whether the integral fallson the "1" or "0" side of the boundary on the vertical voltage axis Urepresenting the magnitude of the integral. The lower magnitude voltageV range along the Y axis represents the encoding of a binary zero at 45°and the higher magnitude voltage range represents the encoding of abinary one at 135°.

The digital signal processor U3' clock is synchronized by ID/S' of FIG.5A or FIG. 5D to the incoming data which permits it to integrate in awindow around the exact angular phase of where the modulation is placed.The sampling of the voltage, may begin at 35° and end at 55°. In the 20°window, the digital signal processor U3' computes hundreds of sampleswhich are integrated. The size of the window and the number of angularpositions of the subcarrier which are modulated may vary in practicingthe invention with much higher numbers of bits modulated per quadrant ofthe subcarrier being possible than illustrated in FIG. 6A.

FIG. 14B illustrates a simplified example of computing the integral ofthe waveform at 45° in FIG. 14A where only eleven samples are takenwhich have an integrated value of eight. Once the integrated value isobtained, the digital signal processor U3' looks in a prestored lookuptable as described below in detail in conjunction with FIG. 18 whichpermits a value of zero to be within a numerical integration rangebetween zero and sixteen. In FIG. 14A it can be that the numeric valuefor the data contained at the 135° phase will be greater than sixteen.Therefore, the same integration process and comparison with the range ofprestored values centered in a 20° window around 135° would yield avalue of one at the 135° phase.

The actual values obtained in each step of the integration process willtypically be much higher than the foregoing example of FIGS. 14A and B.The actual values obtained in each step of the integration process willbe dependent upon many variables determined primarily by the receivingcircuitry. The operating voltage, A to D sampling speed, and clock speedof the digital signal processor U3' will all influence the actualnumeric values obtained in this integration process. However, thetransmitted waveform will appear essentially the same for all mobiledata products using the invention. Each of the different received datawaveforms will have different binary values and different binary rangesin their lookup tables.

The integration of a squarewave subcarrier with each half being pulsewidth modulated with four bits (numerical widths varying between one andsixteen), as illustrated in FIGS. 6B and 9, is described as follows withreference to FIG. 15. In this simplified example, the digital signalprocessor U3' takes ten samples of the detected subcarrier where inactual practice hundreds of samples would be taken. The previouslystored sample values representing the waveform are processed by thedigital signal processor U3' to integrate the area under the waveform.In actual practice, the number of samples will be dependent upon thesampling speed of the A to D converter and the clock speed of thedigital signal processor U3'. In this example, there is a fixednumerical value assigned to the X axis and a value that isrepresentative of the received voltage V of the waveform on the Y axis.The digital signal processor U3' uses these values to calculate anumeric sum for each sample. These numerical values of each sample arein turn summed to provide a summation or integration of all of thesamples under the pulse width modulated waveform. The summation value ofFIG. 15 is ninety. This number would be much larger in actual practice.The digital signal processor U3' then uses its prestored program to lookup the range of summation values stored in its lookup tables asdescribed below in detail in conjunction with FIG. 18. Because of signaldistortions, which are always present in a wireless environment, thelookup tables contain finite boundaries or numeric ranges that pertainto each of the sixteen possible binary combinations. FIG. 15 illustratesthat for a value of ninety the four bit combination of zero, one, zero,one is obtained. Any summation within the numeric range of eighty-fiveto ninety-five is represented in subsequent signal processing of theserial information by the aforementioned four bit combination.

Like the example discussed above involving multiple phase modulation,products using digital modulation will have prestored ranges dependingupon the design of the receiving circuitry. If very low receivedvoltages are summed, smaller summation ranges are obtained.

FIGS. 16A and 16B illustrate the sample processing of a half of a cycleof a pulse width modulated squarewave to eliminate the effects of noisewhich introduces error into the calculation of the integral of the halfa cycle as described above in conjunction with FIG. 15. FIG. 16A showsthe leading edge of the waveform that contains a noise transient. Thisnegative going transient is not a portion of the actual pulse widthmodulated data and introduces error in the integration of the waveformby the digital signal processor U3'. Sample signal processing isutilized to assist in the reconstruction of the pulse width modulatedwaveform to remove transients that are caused by noise and otherman-made interference. While the digital signal processor U3' isdecoding the pulse width modulated waveform to transform the serialinformation into a series of numerical values each representing therange containing the calculated integral of each selected part, thenumeric sample values encoded as groups of bits are stored in atemporary RAM memory such as U4'. As illustrated in FIG. 16A, each ofthe samples is converted to a numerical value by an A to D converter orcomparator associated with the digital signal processor. The ROMassociated with the digital signal processor stores a table of numericalranges which represent valid sample values over the duration of a partof the cycle of the subcarrier which are to be included in theintegration of the subcarrier. As illustrated, the numerical ranges arebased upon expected ranges which occur for a particular receivingcircuitry design that represent signal levels which occur when the halfof the subcarrier cycle is at its high or low level. For example, theillustrated transient is outside the numerical range of sample valueswhich represent valid samples when the pulse width modulated carrier isat its high level. When a sudden or dramatic change in the A to Dvoltage reading occurs, as described above by the comparison of thesample value with a range of valid sample values, the digital signalprocessor U3' is triggered to perform a series of calculations. Becauseof storage in a Ram buffer area of the sample values necessary tocompute the integral, one or more sample values immediately before andimmediately after a transient are used for signal processing to providea replacement sample value. The replacement information is a function ofsample values adjacent the sample value which is replaced. In one formof possible signal processing to replace the noise with a sample valuemore accurately representing what the actual sample values should havebeen, the immediately preceding and succeeding sample values are addedand divided by the number of samples to be averaged to yield areplacement sample value average to fill in the erroneous sample causedby the noise transient. The resulting waveform appears in FIG. 16B as asmall step that makes the resulting waveform more representative of thepulse width modulated waveform. In this example, if the preceding samplevalue from the A to D converter was 1 volt and the following reading was1.1 volts, the replacement sample would have a value of 1.05 volts. Thisis considerably more accurate than the actual received pulse widthmodulated waveform that would have had a near zero value for thesampling period.

FIGS. 17A and B illustrate the reconstruction of a data waveform whenmodulation of the sinusoidal subcarrier is used as illustrated in FIGS.6A and 8. In this example, the 45° phase is being processed which ismodulated with binary information having noise riding on the data signallevel. As discussed above in conjunction with the processing of a pulsewidth modulated waveform having noise riding on the data signal level,the digital signal processor U3' stores the sample values in thetemporary RAM buffer. As illustrated in FIG. 17B, each of the samples isconverted to a numerical value by an A to D converter or comparatorassociated with the digital signal processor. The ROM associated withthe digital signal processor U3' stores a table of numerical rangeswhich each represent valid sample values over the duration of a part ofthe cycle of the subcarrier which are to be included in the integrationof the subcarrier. As illustrated, the numerical ranges are based uponexpected ranges which occur for a particular receiving circuitry designthat represent signal levels which occur around the modulated phases ofthe subcarrier. For example, the illustrated transients are outside thenumerical ranges of sample values which represent valid samples when thesubcarrier is modulated with a one or zero as illustrated in FIG. 7 inthe 20° window centered at 45°. When a series of voltage readings do notconform to the rate of rise or slope that would have been typical ofvalid binary encoding phase data, the signal processing is triggered toattempt to correct the data. The previous and subsequent A to Dconverter voltage readings are added together and divided by the numberof readings to substitute a more accurate sample value which wouldtypically be present in the absence of noise for the sample valuerepresenting noise. As can be seen in FIG. 17B, the modified signalwaveform resembles more closely and more accurately the actualtransmitted data. When the digital signal processor U3' now begins theintegrating process to determine if the phase information contained atthe 45° phase sample is a binary one or zero, the accuracy of theintegration (and, therefore, the determination) is considerably moreaccurate. FIG. 14A illustrates what the data would look like whensubcarrier modulation is being transmitted. In FIG. 14A it can be seenthat the binary value of the data at the 45° phase is a binary zero andthe binary value of the data at the 135° phase is a binary one. When thereceiving circuitry in a receiver, transceiver or associated with a basestation is be located in an extremely noisy environment, theaforementioned sample signal processing will serve to enhance andreconstruct the received data and will reduce the amount of errorintroduced by noise in the integrating process.

FIG. 18 illustrates the processing of the digital signal processor U3'which numerically compares each of the calculated integrals with aplurality of stored ranges which ranges each represent one of aplurality of possible numerical values that the selected part (one-halfof a squarewave subcarrier or angular position of an analog subcarrier)may encode to identify a stored range numerically including thecalculated integral and substituting for the at least one selected partof each of the cycles the one of the plurality of numerical valuesrepresentative of the identified stored range including the calculatedintegral with each numerical value encoding at least a part of a dataunit of the frames of information after the integrated value of the atleast one selected part of a cycle of a subcarrier for a plurality ofcycles has been determined which includes the integration of FIGS. 14Aand B and 15 and the noise transient reduction of FIGS. 16A and B and17A and B. The digital signal processor U3' takes the obtainedintegrated value and looks up the resulting binary value of a single bitor a group of bits depending if the subcarrier modulation is analog ordigital or equivalent in the prestored lookup tables. With reference toFIG. 18, the processing proceeds from step 151 where integration iscompleted to decision point 153 where a determination if the modulationis analog (multiple phase at spaced apart angular positions of thesubcarrier of FIG. 6A) or digital (pulse width modulation of halves ofthe squarewave subcarrier of FIG. 6B) is made. If the answer is "yes" atdecision point 153, processing proceeds to step 155 where the lookuptables for processing the integration of pulse width modulation of ahalf of a cycle of the subcarrier are accessed. The stored ranges areeach 100 in magnitude. Processing proceeds to step 157 where adetermination is made if the value of the integration is less than 900.A value at decision point 157 of less than 900 indicates that the pulsewidth modulated waveform has an inherent problem making the comparisonprocess invalid. If the answer is "yes" at decision point 157, theprocessing proceeds to step 159 where an error code is stored in abuffer within the RAM U4'. Processing proceeds from step 159 to decisionpoint 161 where a determination is made if all of the stored integrationvalues which are being group processed have been processed. If there aremore values to be processed, the program loops back to step 155.Otherwise, the processing is complete. If the answer at decision point157 is that the integral value is not less than 900, processing proceedsto decision point 163 where a determination is made if the integral isless than 1100. If the answer is "yes" at decision point 163, a four bitbinary value of 0000 is stored at step 165 in the buffer RAM U4' whichrepresents at least a part of an information unit of the serialinformation. Processing proceeds to decision point 167 where adetermination analogous to decision point 161 is carried out. If theanswer is "no" at decision point 163, processing proceeds to decisionpoint 169 where a decision is made if the integral value is less than1200. If the answer is "yes" at decision point 169, processing proceedsto step 171 where a binary value of four bits of 0001 is stored in thebuffer RAM U4' The processing proceeds to step 173 which is analogous todecision point 167. The broken line labelled "ONE TEST FOR EACH BINARYVALUE" indicates testing of the integral values for a series ofincreasing ranges which are increased in steps of 100 to determine ifthe binary values representing four bit groups between 0010 and 1110should be stored in the buffer RAM U4'. Decision point 175 representsthe last test where a determination is made if the integration value isless than 2600. If the answer is "yes", the processing proceeds to step177 where the four bit binary valve 1111 is stored in the buffer RAMU4'. The processing proceeds from step 177 to decision point 179 whichis analogous to decision points 167 and 173. If the answer is "no" atdecision point 175, processing proceeds to step 181 where an error codeis stored in the buffer RAM indicating that the integration value isgreater than that which would be predicted by the prestored values(ranges) for each of the sixteen binary combinations. The processingthen proceeds to decision point 183 which is analogous to decisionpoints 167, 173 and 179.

If the answer to decision point 153 is "no", the processing proceeds tostep 185 where the range for the binary values of one and zero areaccessed for comparison with the integration value obtained at step 151for the modulated separated angular phases of the subcarrier. The binarylookup tables are different than the pulse width modulation tables andare representative of the boundary between "1" and "0" values present inFIG. 14A for each of the separated angular phases which are modulated onthe subcarrier. The integrated value falls within a range on one or theother side of the boundary for each separated angular phase whichcontrols whether the modulation of the subcarrier at the separatedangular positions is decoded as a one or a zero. When the integrationprocess is completed, the processing compares the integrated value withranges that define on which side of the boundary the actual integrationlies. In this process the processing proceeds to decision point 187where a determination is made if the value of the integral is less than350. If the answer is "yes" the processing proceeds to step 189 where abinary zero is stored for the angular phase in the buffer RAM U4'. Theprocessing proceeds to step 191 where a determination is made if morevalues are to be processed. This step is analogous to steps 161, 167,173, 179 and 183 previously described. If the answer is "no" at step187, processing proceeds to decision point 193 where a determination ismade if the value of the integral is less than 700. If the answer is"yes", processing proceeds to step 195 where a binary one is stored inthe buffer RAM U4'. The processing proceeds from step 195 to decisionpoint 197 where a decision is made analogous to decisions 161, 167, 173,179, 183 and 191 described above. If the answer is "no" at step 193, theprocessing proceeds to step 199 where an error code is stored in thebuffer memory analogous to steps 159 and 181 as previously described.The processing proceeds from step 199 to decision point 201 which isanalogous to decision points 161,167, 175, 179, 183, 191 and 197.

The contents of the buffer RAM U4' store a group of binary valuesrepresentative of individual bits when multiple phase modulation atseparated angular positions is modulated on the subcarrier and groups ofbits representative of the possible modulated numerical values whenpulse width modulation is modulated on the subcarrier. The contents ofthe buffer RAM U4' store the detected serial information containing thedetected FRAME GROUPS of FIGS. 5A-C, FIG. 5D or modifications thereoffor subsequent processing by the signal processor U3'. Any errors causedby fading or other transmission fault which renders one or more bits ofindividual frames erroneous and uncorrectable or a sequence of framesincluding whole frame groups are contained at this time in the bufferRAM U4'. The processor U3' detects when an error is present byprocessing the error correction code embedded in the frames of thestored serial information as described below.

Although the previously described sample processing will serve to removetransients that may produce the decoding of erroneous data when largeerrors are introduced into the calculation of the integrals, it is stillpossible that the integration of the data modulated on the subcarrier ata particular phase would result in an erroneous detection. Manydiscriminators in radio receiving electronics have finite voltage limitswhen data is being detected. When receiving circuitry in a receiver ortransceiver are designed for low voltage operation, the recovered datawill be between zero and one volt in amplitude. However, in many typesof discrimination there are particular combinations of interferences(typically, adjacent channel interference) that can cause a noise signalto be much greater in amplitude than the one volt level. These spikes ornoise may be as high as two or three times the expected amplitude andnot be representative of a true received data signal. The problem ismore prevalent when multiple phase data is being decoded as this type ofadjacent channel noise that is detected by the discriminator contributesgreatly to distorting of the detected waveform and may change a binaryzero to a binary one and a binary one to a value much greater than whata binary one is predicted to be. As previously described, the samplesignal processing has finite limits on an amount of data interpretationthat can be accomplished. Specific high and low boundaries must beplaced in the lookup tables to prevent such data interpretation frombeing considered invalid. This is the reason for finite boundary valuesas discussed above in processing both multiphase and pulse widthmodulation of the subcarrier. The boundaries and the need for suchboundaries will be dependent upon the receiving circuitry design of theparticular product. Therefore, the boundaries represented by decisionpoints 159, 181 and 199 may or may not be necessary in the receivingcircuitry of a particular multiple phase or pulse width modulationapplication of the receiving circuitry which can make steps 159, 181 and199 unnecessary. If the receiving circuitry is based exclusively uponeither the multiphase or pulse width modulation protocol, decision point153 may be omitted with only the necessary part of the processing forthe particular protocol being included in the receiving circuitry.

FIGS. 19A and B depict the general operation of the receiving circuitryas described above in FIG. 13. The flowchart depicts frequencysynthesized receiving and battery saving techniques that are used withcurrent receiver designs. Point 200 represents the power oninitialization routines. When the user first turns on the power to thereceiving circuitry at point 202, the resident control processor U7'starts an initialization process and self-testing diagnostics to insurethat the receiving circuitry is fully functional. These diagnosticsinclude the turning on and preprogramming of a frequency to the phaselock loop (not illustrated) and verification that the phase lock loop atpoint 204 can lock on a test frequency or the preprogrammed operatingfrequency, and a measurement of the battery voltage. The initializationroutine also includes a verification of receiving circuitry'spreprogrammed ID as contained in the encoded ID digits of the ID FRAMEGROUP of FIGS. 5A and B and a visual test of the liquid crystal displayby scrolling a test message for the user to observe.

Upon completion of the power on initialization, the receiving circuitryinitializes its sampling routine of the radio channel. The controlprocessor U7' first turns on the receiving circuitry power and loads thephase lock loop with the operating channel frequency data. The controlprocessor U7' then waits for a channel lock verification from the PLLcircuit prior to determining if carrier is present on the samplechannel. When the lock condition is detected at point 206, the controlprocessor U7' then tests for the presence of carrier at decision point208. If there is no carrier present on the received radio channel, it isunnecessary for the control processor U7' to continue the receivingprocess, and it then powers off the receiving circuitry at point 210.Processing then stays in a loop including 212, 214, 202, 204, 206, 208and 210 in which incrementing a 430 millisecond timer in one millisecondincrements at points 212 and 214 occurs. During this time the controlprocessor U7' is also looking for external keypress or serial portactivity. If the user initiates a keypress function at decision point216 (e.g., to read or display a message), the control processor U7' thenexecutes the respective service routines to display the message. If anexternal peripheral device, such as the laptop PC 118, via the serialport 120 indicates that some activity is desired, the control processorU7' again goes into the user service routine to service the request.

Upon completion of the 430 millisecond time out, the control processorU7' then turns on the receiving circuitry power at point 202 and loadsthe PLL with frequency data at point 204. This channel samplingconserves the battery of the receiving circuitry of the receiver ortransceiver.

When carrier is detected, the control processor U7' then turns on thepower to the digital signal processor U3' and flash A to D converter atpoint 218. An initialization sequence is then initiated at point 220 bythe control processor U3' and the digital signal processor U3' thensearches for the presence of the multiple phase or pulse widthmodulation preamble information at point 222. If no preamble is present,the control processor U7' then proceeds to turn off the receivingcircuitry and digital signal processor power and the four hundred thirtymillisecond timer sequence is again initiated. If preamble is present atdecision point 222 during the digital signal processor U3' samplingtime, the digital signal processor then searches for a preamble match atdecision point 226 identical to that contained in the ID FRAME GROUPS ofFIGS. 5A or FIG. 5D. If the preamble does not match that of thepreprogrammed ID of the receiving circuitry of the receiver ortransceiver, the control CPU then initiates the orderly power offsequence at point 224.

If a preamble ID match is found at decision point 226, the controlprocessor U7' then initiates the command to narrow the receivingcircuitry bandwidth at block 228. During the initial sampling forpreamble by the digital signal processor U3', the bandwidth has beenbroadened to permit rapid synchronization time. Being programmed with awider bandwidth effectively serves to decrease the synchronization timeof the digital signal processor U3' to the preamble data. When thedigital signal processor U3' has been synchronized to the preamble atdecision point 226, the bandwidth is then narrowed at point 228 toreduce the potential for noise interference and increase the integrityof the received information. The next process is for the digital signalprocessor U3' to decode the command CB of the ID FRAME GROUPinformation. This is followed by the decoding of the balance of the IDcode of the receiving circuitry that is sent to the receiver ortransceiver. If the control CPU U7' does not receive an ID match atdecision point 232, it checks to see if the message being sent containsthe batch command (command CB) at decision point 234 indicating that oneor more messages to different ID code receivers or transceivers is beingsent. If a batch command is detected at decision point 234, the controlCPU U7' continues to monitor the message stream looking for an ID codematch.

If an ID match has not occurred and a batch command CB has not beenreceived, the control CPU U7' then initiates the orderly power downprocess at point 224 and continues the channel sampling sequence.

If the ID does not match and a batch command CB has been received, athird test is conducted to determine if either a message end of filecommand is present in the SHORTENED EOF FRAME GROUP of FIGS. 5C or D atdecision point 236 indicating that no more messages are to be receivedwithin that preamble group or alternatively at decision point 238 thatcarrier has disappeared from the radio channel. If the answer is "no" atdecision point 238, control CPU U7' then again initiates the orderlypower down process at point 224.

If the ID matches that of the receiving circuitry of the receiver ortransceiver, then the control processor U7' begins the decoding at point240 of the Command CB and storage thereof. At block 242, the informationof the serial information is decoded and stored in RAM U8'. The controlprocessor U7' continually monitors for the end of file command EOF inthe SHORTENED EOF FRAME GROUP of FIGS. 5C or FIG. 5D at decision point244. If the end of file command EOF has been received at decision point244, the control processor U7' then initiates the alerting sequence thatis indicated by the end of file command. This may be a visual alert, anaudible alert, or a mechanical alert (e.g. vibrator as indicated atblock 246). Upon completion of the alert sequence, the control processorU7' again re-enters the orderly powerdown process of point 224 andcontinues channel sampling and scanning of the receiver's ortransceiver's push buttons or serial port for activity.

If the end of file command EOF was not received, the control processorU7 then checks to determine if carrier is present at decision point 248.If carrier was not present, it indicates to the control processor U7'that faded information has occurred and the last end of file command EOFwould not be received and then initiates the orderly power down processat point 224. If the end of file command EOF was not received and yetradio carrier remains present, it then continues the decoding andstorage of the message material.

FIG. 20 illustrates a configuration of a two-way data transmittingsystem in accordance with the present invention. A protocolencoder/decoder network switch 602, which may be in accordance with FIG.7, interfaces through the public switched telephone network PSTN via atelephone office 604 to a plurality of different types of informationsources. The different types of possible information sources may be a PC606, an E-mail source 608 and a data service 610. The aforementionedinformation sources are only exemplary of information which may beinputted to a two-way data transmitting system. The protocolencoder/decoder network switch 602 also is connected to a plurality ofbase stations 612 which are identified by the reference numerals "1"-"N"inside the rectangular boxes labelled "base station" to identify avariable number. Each base station 612 has an antenna 614 whichfunctions both as a transmitting and receiving antenna. Carrier 616 isprovided to the base stations which is modulated with an analog ordigital subcarrier in accordance with FIGS. 6A 6B, 8 and 9. Thesubcarrier is modulated with the FRAME GROUPS of FIGS. 5A-C, FIG. 5D ormodifications thereof. Two-way radio communications are broadcast on themodulated carrier between the base stations 612 and a plurality ofmobile devices 618 each of which have a transmitting and receivingantenna 620. The two-way data transmitting system mobile devices 618 maybe without limitation in practicing the invention, a mobile datatransceiver A, portable PC, personal digital assistant (PDA) which maytake the form of a hand-held computer, a wireless fax and another mobiledata transceiver B which process the serial information stream asdiscussed above.

A two-way data transmitting system 600 in accordance with the inventionhas three basic call sequences which occur in providing mobile dataservice. The first sequence is a land-to-data mobile call in which thecall originates from the wireline telephony network PSTN through thenetwork switch 602 to a base station where it is radio broadcast to amobile device 618. The second call sequence is a mobile device 618originating a call to the wireline telephony network PSTN. The mobiledevice 618 originates the call which is transmitted via wirelessbroadcast 616 to a transceiving facility 612, 602 which is in turnconnected to the wireline network. The third call sequence is a mobiledevice 620 making a call to another mobile device which is theequivalent of a cellular mobile to cellular mobile call in that bothunits are mobile or portable and the call from the originating mobiledevice is directed via wireless broadcast through the land stationfacility, processed by the protocol and encoder/decoder of the networkswitch 602 and is relayed back to the recipient mobile device viawireless broadcast. An example of this call sequence is from mobile A tothe base station 1 through the protocol encoder/decoder of the networkswitch 602 back through the base station "N" to the mobile B. In each ofthese call sequences it should be understood that the explanation whichrefers to data devices A and B may be any of the devices described aboveas mobile devices.

With reference to FIG. 20, a land to mobile data message may originatefrom any number of devices. The data message may originate from the PC606, the E-mail system 608 or the data service 610 that requires amessage to be sent to a wireless destination. Such data services may bestock quotes, sports quotes, news services, map services, weather ortraffic information and any other number of public or non-publicservices that need to be conveyed to an individual or multiple mobiledata transceiver. The call sequence first begins on the left-hand sideof FIG. 20 from any one of the data origination devices as described.For purposes of this example, the call originates from the E-mailservice 608 to send a memo to the mobile A shown on the right-hand sideof FIG. 20. The E-mail service 608 via the PSTN through the telephoneoffices 604 routes the call to the protocol encode/decoder of networkswitch 602 by dialing the corresponding telephone number of mobile A.Upon receipt of the call, the network switch 602 connects a modem to thetelephone line to permit the E-mail message from the E-mail source 608to be transmitted and received by the network switch 602. At this pointit should be noted that the protocol encoder/decoder of network switch602 functions to generate the serial information as described abovewhich carries the message content originated from the E-mail source 608as well as other protocol information including error correction codeand frame identification information with the format of FIGS. 5A-C, FIG.5D or modifications thereof. The network switch 602 looks up detailedinformation concerning the mobile A data transceiver. This informationincludes the A mobile's identification number, types of service that themobile is registered to have, the transmission format and the particularbase station or group of base stations that the A mobile currentlyresides on. Upon completion of this information look-up, the protocolencoder/decoder section of the network switch 602 selects an appropriateencoding module to perform encode of the subcarrier with the informationformatted in accordance with FIGS. 5A-C, FIG. 5D or modificationsthereof and relays the information via the "link" to base station "1".The "links" that are shown in FIG. 20 can be any one of a number ofdifferent communications media. It may be microwave, dedicated wireline,fiber optics or any other typical voice grade line. Control signals aresent by the network switch 602 to the base station "1" to turn on itstransmitter 616 to begin the data transmission process which includesbroadcast of the channel carrier 616 modulated with the analog ordigital subcarrier which encodes the information formatted in accordancewith FIGS. 5A-C or FIG. 5D as described above or modifications thereof.The mobile A provides some form of acknowledgment or response and mayalso be involved in interactive data communications. Interactive datacommunications could be an on-line communication between a PC 606 andthe mobile A. Files may be transmitted from the PC 606 to the mobile Awhich are modified or which respond to the data by returning atransmission of the data via base station "1", the network switch 604and through the telephone office 602 in the PSTN back to the originatingPC 606.

A second sequence is a data mobile to land call sequence. With referenceto FIG. 20, mobile A sends a data message to the land-based PC 606. Themobile A data transceiver enters the message and then initiates thetransmission sequence. The mobile A, which is currently registered atthe network switch 602, identifies and transmits the data message viathe RF link to base station "1". Base station "1" receives the datamessage and forwards the message in real time to the network switch 602when the mobile A initiates the calling sequence to transmit the data.The network switch 602 has been alerted and has received the mobile A'sidentification number. The network switch 602 then looks up in itssubscriber file for data pertaining to the mobile A to determine whattype of protocol encoding and decoding equipment to connect to the basestation "1" port. The network switch 602 also looks up the types ofservice options to which the mobile A has subscribed. The protocolencoder/decoder network switch 602 receives the data message modulatedin analog or digital form on the subcarrier to encode the informationformatted in accordance with FIGS. 5A-C, FIG. 5D or modificationsthereof from the mobile A data where it is decoded by receivingcircuitry resident in the decoder which performs the functions of thereceiving circuitry discussed above including with reference to FIG. 13.In this sequence, the mobile A has also transmitted the correspondingtelephone number for the land-based call to the personal computer 606.The network switch 602 then dials the telephone number of thedestination PC 606 through the telephone office 604 in the PSTN. Acorresponding modem is connected to the PSTN link so that when the PC606 answers, the data can be transmitted to the destination PC 606. Uponcompletion of the data transmission to the PC 606, the network switch602 terminates the call. This explanation basically describes a one-waydata message between the mobile A and the land-based PC 606.

There are other scenarios where the exchange of data may take place. Inthis case, two-way data transmissions occur during the mobile A and thePC 606 upon call set up. This permits real-time or interactive datatransmission to occur between the mobile A and the PC 606. An example ofthis is when the mobile A accesses particular files in the Mobile Auser's office PC 606 to either modify and/or retrieve data from thepersonal computer 606. The mobile A may be a full duplex or simplexmobile depending upon the type of transmitting infrastructure that isavailable for the wireless data service.

The third type of transmission is the data mobile to data mobile callsequence. With reference to FIG. 20, the mobile A initiates the datamessage call by alerting the network switch 602 by sending itsidentification code via the wireless link to base station "1" to theprotocol encoder/decoder of the network switch 602. The network switch602 then qualifies the mobile A's identification number and connects thenecessary type of protocol encoder/decoder of the network switch 602 tothe base station "1" port in order to receive the data message. Themobile A then enters mobile B's identification number (or telephonenumber) and begins the transmission of the data message. The networkswitch 602 looks at the mobile B's customer file to determine what radiochannel and type of protocol decoder the mobile B transceiver has. Inthis case, mobile B is located on base station "N". Upon receipt of thedata message from the mobile A, the network switch 602 temporarilystores the message in a buffer file of memory and then begins thesignalling process to contact the mobile B. The mobile B'sidentification number is transmitted alerting the mobile B data that amessage is about to be transmitted. The network switch 602 via basestation "N" connects the necessary type of protocol encoder/decoder toformat the information in accordance with FIGS. 5A-C, FIG. 5D ormodifications thereof and modulates the analog or digital subcarrier andtransmits the modulated subcarrier to the mobile B when the subcarriermodulates carrier 616. This example is essentially a one-waytransmission of a data message from mobile A to mobile B.

There are variations of this call sequence such as an interactive datacommunications between mobile A and mobile B. A real-time interactiveexchange of data may occur between mobile A and mobile B. Both mobileunits then via real-time transmission exchange data between each other.This may be a form of interactive short text messages exchanginglocation or other information. In this configuration, both data mobileunits remain actively transmitting or both transmitting on acorresponding base station with the network switch 602 acting as theencoder and decoder of serial information and buffering and forwardingthe serial information between each unit. Another variation to thismobile communications sequence is for mobile A to send data to thewireless fax, PDA or a portable PC with a wireless link. Any number ofdata communications can be exchanged between each of the mobile devices618 to any other type of mobile device. One type of transceiver whichmay be used in practicing the invention is described below in FIG. 21.The transceiver performs the functions of the transmitting and receivingcircuitry described above in FIGS. 12 and 13.

FIG. 21 illustrates a block diagram of a transceiver 700 in accordancewith the present invention such as the mobile transceivers describedabove with reference to FIG. 20. The transceiver 700, as illustrated, isfull duplex (being able to transmit and receive at the same time) as istypical in many wireless data transceivers. There are variations fromduplex, such as simplex mode where the transceiver 700 transmits andreceives on the same frequency or in a duplex "burst" mode where thetransceiver only transmits for short burst type of transmissions toconserve battery power.

The transceiver is a dual conversion frequency synthesized device. Thereceived signal is transmitted from antenna 702 through aduplexer/combine 704 which functions to couple the antenna to the radioreceiver and provide isolation from the transmitter power amplifiers 746to prevent desensitization of the receiver and to utilize a singleantenna for both the transmission and reception of information. The RFamplifier 706 may contain one or more stages depending upon theoperating frequency of the transceiver 700. The received signal thenflows to a filter and first mixer 708 at which the signal is mixedfollowing by intermediate filtering. The mixing uses the output signalfrom the mixer, voltage controlled oscillator and phase lock loopcircuitry 710 to convert the received signal to the intermediatefrequency. The IF frequency produced at the first mixer 708 may be anynumber of frequencies depending upon the operating frequency spread ofthe transceiver 700. Typical choices for the IF frequency at this pointare 44, 21.4 or 10.7 MHz. After IF filtering, the signal is amplified byIF amps 712 which typically contain a plurality of stages. The signal,as amplified by the IF amps 712, proceeds to a second mixer 714 at whicha signal from mixer oscillator 716 is mixed with the amplified IF signalto produce a lower IF frequency signal. The lower IF frequency signalprogresses to a filter and IF amps 718 where further IF filtering andamplification occurs. The filtered and amplified signal proceeds to adetector or discriminator 720 where the IF signal is demodulated to anaudio frequency signal which contains the analog or digital subcarriermodulated with the information formatted in accordance with FIGS. 5A-C,FIG. 5D or modifications thereof.

Depending upon the format of the transmission protocol (multiple phase,pulse width modulation or both types of modulation of the subcarrier)the detector or discriminator 720 may have numerous configurations thatare well known in the state of the art. The illustrated receivercircuitry may have a standard FM discriminator with the recovered audiofrequency signal being fed to a series of audio frequency amplifiers andfilters 722. All of the above-referenced components represent a standardcommunications receiver known in the art. The operating frequency of thereceiving part of the transceiver 700 is controlled by the mixer,voltage controlled oscillator and phase lock loop circuitry and is underdirect control of the control processor 724. The control processor 724in the transceiver 700 is responsible for numerous functions includingthe direct frequency control of both the receiver and transmittingcircuitry to perform the functions as described below.

The receiving circuitry of the transceiver 700 includes the digitalsignal processor 726 and the control processor 724. The receivingcircuitry performs the processing of the modulated subcarrier to convertthe serial information modulated on the analog or digital subcarrierinto binary information as described above having a format in accordancewith FIGS. 5A-C, FIG. 5D or modifications thereof and, additionally, theprocessing of the serial information converted into binary informationto correct for faded information and produce a reconstructed andresynchronized output as described below.

The digital signal processor 726 has an A to D converter or comparator728 for digitizing signal levels, RAM 730 for storing information asdescribed above in performing the functions of the digital signalprocessor U3' and control processor U7' of FIG. 13, a D to A converter732 for converting digital information to analog, a ROM 734 for storingprestored programming, a CPU 736 for executing the necessary programmingto perform the functions of the digital signal processor U3' andinput/output 736. Furthermore, the digital signal processor 726 mayperform the same functions as the digital signal processor U3' and thecontrol processor 724 may perform the same functions as the signalprocessor U7' as described above with reference to FIG. 13.

The digital signal processor 726 also functions to perform the functionsof the transmitting circuitry of FIG. 12. These functions include thefunctions of CPU U1 and digital control processor U47 of FIG. 12 toproduce the encoded serial information stream modulated on an analog ordigital subcarrier as described above.

The transmitter part of the transceiver 700 has a modulator 740,oscillator 742, multipliers/drivers 744 and power amplifiers 746,duplexer/combiner 704 and an antenna 702. The modulator 740 receives themodulated subcarrier in either analog or digital form, as describedrespectively above with reference to FIGS. 6A and 8 and FIGS. 6B and 9,and converts it to a dynamic range which modulates an oscillator 742which is FM modulated by the output of the modulator 740 to produce alow power RF frequency modulated signal which is FM modulated with thesubcarrier. Depending upon the operating configuration of thetransceiver 700, a separate mixer, voltage controlled oscillator andphase lock loop 748 may exist. In a simplex configuration, the optionalmixer, voltage controlled oscillator and phase lock loop 748 would notbe used and the oscillator would derive this control from the mixer,voltage controlled oscillator and phase lock loop 710. Master oscillator750 is a frequency reference for both the mixer, voltage controlledoscillator and phase lock circuits 710 and 748. The multipliers/drivers744 multiply the frequency of the FM modulated RF signal produced by theoscillator 742 and step up the power to a level such as five watts. Theoutput of the multipliers/drivers 744 is further amplified by poweramplifiers 746. The output of the power amplifiers 746 is appliedthrough the duplexer/combiner 704 to the antenna 702.

The digital signal processor 726 is the heart of the data encoding anddecoding of information by the transceiver 700. As shown, the digitalsignal processor 726 has access to the data control buses of the controlprocessor 724. The digital signal processor 726, in addition to theabove-described functions, serves as a message management processor andto initially synchronize the clock to properly process the bits of theframes of the frame groups, resynchronize the clock and reconstruct oneor more faded frames by processing the serial information as discussedbelow. The serially encoded information which is modulated on thesubcarrier, detected and converted into binary, may be sent to thecontrol processor 724 for storage in the RAM 752. The stored operatingprogram resident in ROM 754 may provide the information necessary topermit the control processor 724 to perform its frequency controloperations, and transmission of the information stored in the RAM 752,transmission of the information to an external serial port 755 and todisplay messages on a resident liquid crystal 756.

Depending upon the power requirements and portability of thetransceiver, power management electronics 758 may also be controlled bythe control processor 724. The power management electronics 758 containcontrol logic that permits the control processor 724 to shut down orcontrol power to various portions of the transceiver. Typically, powerto the transmitter and display will be off during periods of inactivity.The receiver power control will be systematically and periodicallyturned on to sample the received channel for the presence of datainformation. Only when received data is present will the various otherareas of the transceiver be switched on as needed. This type of powermanagement maximizes power conservation and permits the transceiver tobe extremely light weight and portable in operation. The transceiver asdescribed could be a trunk or under dash vehicle mount unit with a poweroutput of ten watts or greater, a small hand-held PDA or notebookcomputer that may only transmit a few watts of power as required.

While the receiving circuitry of FIG. 13 includes the digital signalprocessor U3' and control processor U7', it should be understood thatthe functions of the digital signal processor U3' and control processorU7' of FIG. 13 can be solely performed by the digital signal processor726 or the control processor 724. Furthermore, given the rapid increasein processing speed and processing capability of digital signalprocessors in low voltage, low power integrated circuits, theimplementation of the discrete functions of the digital signal processorU3' and control processor U7' of FIG. 12 into a single processor, suchas the digital signal processor 726, will become increasingly simplerand may be the preferred architecture for performing the processingfunctions of the digital signal processor U3' and control processor U7'instead of having a separate digital signal processor and controlprocessor.

FIG. 22 illustrates a representation of the bits of the fourth frame ofthe DATA FRAME GROUP in accordance with FIG. 5B, including thesynchronization marker S" and the FRAME GROUP # which are stored inmemory of the receiving circuitry after detection of the transmittedcarrier and demodulation of the subcarrier including the processing ofFIG. 18. As explained below in FIGS. 26A-C, the bits of the errorcorrection field are discarded when reconstruction or resynchronizationfollowed by reconstruction is completed which leaves the decoded otherbits for subsequent processing such as outputting of the data units ordata bits. The data bits of FIG. 22 are all valid data bits which do notrequire reconstruction or resynchronization by the receiving circuitryas described below in conjunction with FIGS. 23-27. As is illustrated inFIG. 22, a broken vertical line in the left-hand portion of FIG. 22indicates a break in the time base between bits 2 and 7 in the tenthdata unit. The upper series of numbers in the horizontal row of boxes,as indicated above, identifies bit positions within the fourth frame.The lower boxes containing the legend "V", which are for illustrationpurposes only, identify that the data is valid which signifies that theframe has been processed with the error correction code and no data bitswithin the frame have been found to be invalid beyond the bit errorcorrection capacity of the error correction code. It should beunderstood that the use of the identifying letter "V" is not actuallystored in the memory associated with the digital signal processor. Asexplained above, the error correction code bits have a value which is afunction of the bits of the data units contained in the frame. Theactual value of the data bits and the functionally related error codehas not been shown because it is not necessary for understanding theinvention. The synchronization marker S", as explained above, whichspans eight bits, contains a bit pattern which is representative of aninvalid data unit. With a preferred embodiment of the present inventionin which eight bit ASCII characters are encoded to transmit alphanumericdata, one of the so-called extended ASCII characters between a numericaleight bit value of 127 and 255 is chosen to represent thesynchronization marker S" which does not represent valid data.

The synchronization marker S" provides a fixed position of a group ofbits within each DATA FRAME GROUP which is used to resynchronize theclock of the at least one processor of the receiving circuitry in orderto provide proper processing of groups of bits comprising a frame (e.g.forty five as explained with reference to FIGS. 5A-D) in synchronismwith the timing of the corresponding bits of the frame as formatted andtransmitted by the transmitter. The at least one digital signalprocessor of the receiving circuitry is programmed to detect the uniquepattern of the synchronization marker S" which in FIG. 22 is 11000000.Other unique patterns could also be used. The data stored in the memoryassociated with the digital signal processor is shifted by the digitalsignal processor backwards and forwards by known techniques until theunique bit pattern of 11000000 representing the stored synchronizationmarker S" is located. Thereafter, because the synchronization marker S"marks a fixed position of a group of bits in a FRAME GROUP, the digitalsignal processor is resynchronized and the processing of bits withinframes is locked onto the resynchronized clock timing produced bydetecting the synchronization marker S". Loss of synchronism, asexplained above and below, is determined by at least one data framebeing detected and processed by the at least one processor of thereceiving circuitry to determine that at least one invalid bit exists ina frame which cannot be corrected with the error correction code of theframe thus rendering the frame erroneous in accordance with the priorart. In summary, FIG. 22 illustrates an example of the stored valid datawhich occurs when the error correction code capability of a frame is notexceeded, i.e. all bits are valid in the DATA FRAME GROUP of FIG. 5B.

For example, if the clock timing of the receiving circuitry slippedthree bit positions between FRAME GROUP #3 and FRAME GROUP #12 of FIG.27 as explained below, the digital signal processor by performingshifting of stored bits in memory to locate the synchronization markerin FRAME GROUP #12 shifts the clock timing by three clock cycles. Onceproper clock timing of the digital signal processor is resynchronized,groups of bits corresponding to the number of bits in a frame (e.g.forty five) may be fetched and tested to perform reconstruction ineither a forward and backward direction between the detectedsynchronization marker S" and to and including the at least one framethat contains at least one erroneous uncorrectable bit marking the lossof synchronization to attempt to reconstruct data frames which had beenrendered erroneous by the loss of synchronization as described below inconjunction with FIG. 27.

FIGS. 23-25 illustrate frames which contain at least one erroneousuncorrectable bit. As illustrated in FIGS. 23-25, like in FIG. 22,vertical wavy lines indicate time breaks between bit positions of aparticular frame. The top horizontal row of numbers in FIGS. 23-25, likein FIG. 22, identify particular bit positions within the data units andwithin the error code of a frame within a DATA FRAME GROUP of a formatof FIG. 5B. The bottom series of letters use an "V" to identify validdata, and an "E" to identify erroneous bits which cannot be corrected bythe processing of the bits of the frame with error correction code. Itshould be understood that the use of the identifying letters "V" and "E"are only for illustrative purposes and are not actually representativeof data stored in the memory associated with the digital signalprocessor which, of course, is bit values of one or zero. Again, like inFIG. 22, knowledge of the actual value of the data units and errorcorrection code is not necessary to understand the examples of FIGS.23-25 illustrating erroneous uncorrectable bit patterns comprised ofbits identified by the letter "E". Typically, the BCH 45,24 errorcorrection code has the ability to correct up to two bit errors perframe. With the prior art, the presence of erroneous uncorrectable bitsresults in erroneous information because there was no processingcapability provided in the receiving circuitry receiving a wirelesstransmission of information to recover erroneous bits after the errorcorrection capacity of the error correction code was exceeded as isindicated symbolically by the letter "E" in FIGS. 23-25 and 27.

The error recovery and reconstruction capability of the presentinvention is based upon the processing capability of the at least oneprocessor within the receiving circuitry, which preferably is at leastone digital signal processor, to detect erroneous bit patterns in thefield of the error correction bits after processing of the frame withthe error correction code. The erroneous bit patterns either contain aseries of all zeros or all ones of a number exceeding the bit errorcorrection capacity of the error correction code. That is, if the BCHerror code bit error correction capacity is two bits, a pattern of atleast three or more all zeros or ones would be the object of the patternsearch. Once the error correction code has been processed in each frameand the computation result indicates that at least one erroneous bit ispresent, which signifies exceeding of the error correction capability ofthe error correction code contained in the frame, the processor searchesthe stored bits to look for the aforementioned erroneous bit pattern ofall zeros or all ones located totally within the error correction bitfield. Detection of these patterns and their position within the storedbits in memory by bit shifting or other known techniques aftercomputation by the digital signal processor that at least one erroneousuncorrectable bit is present in a frame is used to determine in whichbit positions the erroneous uncorrectable bits are present. If these bitpatterns are found to be totally within the error correction code bitfield, valid bits outside the bit field of the error correction code(data) are recovered and reconstructed as explained below in conjunctionwith FIG. 23 is successful with the error correction code bits beingdiscarded. If the pattern of all zeros or all ones is not found to betotally within the error correction code bit field, the data bits cannotbe recovered and reconstructed which requires error markers to beinserted for the data units as described below. It should be noted thatthe successful reconstruction of valid data from a frame which containsat least one erroneous uncorrectable bit resultant from processing theerror correction code of the frame is performed in accordance with thepresent invention either during the existence of originalsynchronization produced by the ID FRAME GROUPS of FIGS. 5A and 5D orafter resynchronization by locating the synchronization marker S".

The digital signal processor processes the stored bits of the dataframes within the DATA FRAME GROUPS with the error correction codetherein to determine if the plurality of bits of the data frames do notcontain any erroneous uncorrectable bits which dictates that the data bestored as valid data and the error correction code be discarded. If atleast one erroneous uncorrectable bit signified symbolically by theletter "E" in FIGS. 23-25 which cannot be corrected with the errorcorrection code is located, the digital signal processor processes thestored bits of the frames which contain the at least one erroneousuncorrectable bit somewhere therein to determine if the frames containonly valid data bits in the data field signified by the erroneous bits(the aforementioned multibit pattern of zeros or ones) being totally inthe error correction code field which is illustrated in FIG. 23 whichrenders the data bits valid and the error correction is discarded. As isillustrated in FIGS. 24-25, all of the data bits are not valid assymbolically identified by the letter "E" outside the error correctioncode bit field which renders the data bits of the frames of FIGS. 24 and25 invalid and the data units are stored as error characters. In FIGS.24-25, the pattern of erroneous uncorrectable data bits identified bythe letter "E" is not totally contained in the error correction code bitfield which makes it impossible for the digital signal processor todiscriminate whether or not any of the data units contain valid data. Itis not possible to determine reliably whether any of the eight bit dataunit bit groups in the DATA FRAME GROUPS of FIGS. 24 and 25 are validdata when erroneous uncorrectable bits are not totally present withinthe error correction code, as, for example, being totally contained inthe data units in FIG. 24 or spanning the error correction bit field andthe data unit bit field as illustrated in FIG. 25.

The process of determining whether valid data can be reconstructed fromdata frames containing at least one erroneous uncorrectable bit byprocessing the error correction code of the frame is performed insituations where minor fades or transmission errors occur wheresynchronism is not lost and after resynchronizing is performed. In bothinstances reconstruction of valid data is possible which would have beenlost with use of only the error correction capacity of the errorcorrection code contained in each of the frames as processed inaccordance with the prior art. As illustrated in FIG. 23, only thecircumstance when the error correction code bit field is determined bythe aforementioned pattern recognition capability of the digital signalprocessor to totally contain a successive pattern of all zeros or allones, such at least three successive bits when the BCH code is capableof correcting for a two bit error, represents recoverable andreconstructible data.

After the reconstruction or resynchronization process followed byreconstruction is complete, there no longer is a need for processing theerror correction code bits. Thereafter, the error correction code bitsare discarded and only the bits of the data units are stored in memoryfor further processing to output useful data units.

FIGS. 26A-26C illustrate the processing performed by the at least onedigital signal processor of the receiving circuitry, such as the digitalsignal processor of the receiving circuitry of FIG. 13 of a transmissionformatted in accordance with FIGS. 5A-C. Processing begins at point 800where the digital signal processor fetches a frame of forty five bitsfrom the associated memory. Processing proceeds to point 802 wherein thedata bits of each data unit within the frame are processed with the BCHerror code polynomial stored in the associated digital signal processortemporary buffer and the results, including the BCH error code, aresaved in memory for subsequent processing as is explained below and asillustrated in, for example, FIGS. 23-25 and FIG. 27 explained below.Processing proceeds to decision point 804 where a determination is madeif a bit error is present in the frame by processing the BCH code. Sucherrors do not necessarily, at this point, exceed the bit errorcorrection capability of the BCH code. If the answer is "no" at decisionpoint 804 that processing of the BCH code does not reveal an error inthe frame, processing proceeds to decision point 806. At decision point806, a determination is made of whether or not the synchronizationmarker S" as illustrated in FIGS. 5A and 5B is present. If the answer is"no", processing proceeds to decision point 808 where a determination ismade if an EOF marker is present as illustrated in the SHORTENED EOFFrame Group of FIG. 5C. If the answer is "no" at decision point 808,processing proceeds to point 810 where each of the data units within theframe are stored. With reference to the organization of data bitsillustrated in FIG. 5B, each of the three data units comprised of eightbits in each frame is stored in the memory associated with the digitalsignal processor. If the twenty four data bits within the frame do notdefine an integral number of data units, such as a fraction of a dataunit or an integer plus a fraction of a data unit, those bits are storedwithin the memory. As has been explained above, the choice of how manybits comprise a data unit is made to optimize transmission andprocessing efficiency which, as stated in the examples described above,is based upon alphanumeric data being transmitted as defined by eightbit characters. Processing proceeds to point 812 where a data unitcounter is incremented by the number of data units per frame which, inthe example given above, would be an incrementing by three. Processingproceeds to decision point 814 where a determination is made of whetheror not the digital signal processor associated memory is empty in thatno frames of bits are stored therein. If the answer is "no" at decisionpoint 814, processing proceeds to decision point 816 where adetermination is made if all of the frames have been read from memorywhich comprise the transmission including the first DATA FRAME GROUP andending with an SHORTENED EOF DATA FRAME GROUP. If the answer is "no" atdecision point 816, processing proceeds to point 818 where a next framestored in the associated digital signal processor memory is fetched.Thereafter, processing proceeds to decision point 804 as describedabove. If the answer is "yes" at decision point 816, processing proceedsto point 820 where the digital signal processor buffer section of memoryis processed to clear the memory for processing for the nexttransmission of information. If the answer at decision point 814 is"yes", processing proceeds to decision point 822 where a determinationis made if a batch command CB is present in the ID Frame Groupsillustrated in FIG. 5A. If the answer is "yes" at decision point 822,reception continues as described above in accordance with the generalprocessing performed by the receiving circuitry as described above. Ifthe answer is "no" at decision point 822, processing ends. If the answeris "yes" at decision point 808, processing proceeds to decision point824 where a determination is made if End Of File Data, as illustrated inFIG. 5C, is stored in the digital signal processor memory. If the answeris "yes" at decision point 824, processing proceeds to decision point814 as described above. If the answer is "no" at decision point 824,processing proceeds to point 826 where the End Of File Data is stored inthe digital signal processor buffer section of memory. If the answer is"yes" at decision point 806 that a synchronization marker S" is presentin accordance with the FRAME GROUPS of FIGS. 5A or 5B, processingproceeds to decision point 828 where a determination is made is a dataunit counter equal to ten. As is illustrated, the data unit counter isset to cycle between the number of data units contained in the frames ofa DATA FRAME GROUP as illustrated in FIG. 5B. However, it should beunderstood that the data unit counter could alternatively be set tocycle between the number of frames in a data frame group with the fulltwenty four bits being considered a single data unit. If the answer is"no" at decision point 828, processing proceeds to point 830 where dataunit error markers are inserted for each missing data unit up to ten.The purpose of the data unit error markers is to fill in missing dataunits contained in the frames of data which have not been stored whenthe data unit counter equals ten. The data unit error markers may be anencoded "*". If the data unit counter is determined to be equal to tenat decision point 828, or the processing has proceeded to point 830, asdescribed above, processing proceeds to point 832 where the FRAME GROUP# of FIGS. 5A and 5B is read. Processing proceeds to decision point 834where a determination is made if the FRAME GROUP # which has been readat point 832 is one unit higher than the previous FRAME GROUP #. If theanswer is "yes" at decision point 834, processing proceeds to point 836where the previously stored FRAME GROUP # is incremented by one to agreewith the currently read FRAME GROUP. As is described below, the purposeof storing the FRAME GROUP # is to provide a basis to calculate thenumber of frames which are involved with a loss of synchronism betweenthe determination of where synchronization is detected as being firstlost by one or more successive frames being calculated to contain one ormore erroneous uncorrectable bits and when a synchronization marker S"is first detected in a subsequently transmitted DATA FRAME GROUP so asto insure complete reconstruction processing after resynchronization isestablished by detecting the resynchronization marker S". Once the FRAMEGROUP # of a FRAME GROUP containing frames which contain one or moreerroneous uncorrectable bits is known, and the FRAME GROUP # of thesubsequent DATA FRAME GROUP in which a synchronization marker isdetected to perform resynchronization, the digital signal processor cancalculate how many frames are contained between the detection of theloss of synchronization and the detection of the subsequentlytransmitted synchronization marker to complete reconstruction of theseframes to recover as much valid data as possible by the subsequentprocessing revealing either the error correction code bit correctioncapacity of a frame is not exceeded or even if the error correction codebit capacity is exceeded, the erroneous bits are determined to betotally within the bit field of the error correction code. If the answeris "no" at decision point 834, the processing proceeds to decision point838 where a decision is made whether the FRAME GROUP # is lower. If theanswer is "yes" at decision point 838, processing proceeds to point 840where the digital signal processor buffer is cleared as a consequence ofthe drop in detected FRAME GROUP # which is indicative of a fade whichhas a duration spanning the SHORTENED EOF FRAME GROUP in FIG. 5C intoanother transmission which must start with a lower sequence of FRAMEGROUP #'s. Processing proceeds to point 842 where the remaining dataunits of the frames of the FRAME GROUP are filled with error markersbecause of the fault having spanned the previously detected FRAME GROUP# into a FRAME GROUP of another transmission. Those frames in the DATAFRAME GROUP which were detected prior to the subsequent detection of alower FRAME GROUP # have error markers stored therein. Processingproceeds from point 842 to the end of processing because of the endingof the transmission without detection where the transmission endoccurred by detecting the SHORTENED EOF FRAME GROUP of FIG. 5C. If theanswer is "no" at decision point 838, processing proceeds to point 844where a determination is made of how many FRAME GROUPS have been missed.This determination is made by comparing the number of FRAME GROUPS whichare missing between the previously detected FRAME GROUP # and thecurrently detected FRAME GROUP #. For example, if the FRAME GROUP #'sdiffer by three, the number of FRAME GROUPS which have been missed isequal to three which is used at point 846 to fill in the data units witherror markers in each missing FRAME GROUP. Processing proceeds to point848 where the FRAME GROUP counter is updated by the number of missingFRAME GROUPS as calculated at point 844. Thereafter, processingcontinues to decision point 808 as described above. If the answer is"yes" at decision point 804 that a BCH error is present, then processingproceeds to decision point 850 where a determination is made if the BCHerror exceeds the error correction capability (e.g. 2 bits) of the BCHcode contained in a frame. If the answer is "no" at decision point 850,which is indicative of a correctable data error being present,processing proceeds to point 852 where each of the data units within aframe is corrected using the error correction code present in thedetected frame. This correction process is the conventional process usedby BCH or other error correction codes. Processing continues to decisionpoint 854 where a determination is made if the data units contain asynchronization marker S" which is indicative of proper synchronizationbeing present in either the ID or DATA GROUP frames of FIGS. 5A and 5B.If the answer is "yes" at decision point 854, processing proceeds backto decision point 828 as described above. If the answer is "no" atdecision point 854, processing proceeds to point 856 where the bits ofthe frame are stored as valid data units. Processing proceeds to point858 where the data unit counter is incremented by a number of data unitsin a frame which in the current example is equal to three. Processingproceeds back to decision point 814 as described above. If the decisionis "yes" at decision point 850, which is a condition indicative of datareconstruction being required, processing proceeds to point 860 wherethe next frame is fetched from the digital signal processor buffer. Thebits of the frame are processed as described above at point 802 with theBCH error code polynomial. The resultant processed bits are stored inthe digital signal processor temporary buffer including the BCH errorcode being saved to provide a basis for data reconstruction both byanalyzing with pattern recognition techniques, as described above, ifthe erroneous uncorrectable bits in a series of all zeros or all onesare totally contained within the BCH error correction code bits in asituation where synchronization is not lost as illustrated, for example,in FIG. 23 and further, in the situation, as described below inconjunction with FIG. 27, where synchronization is lost and isresynchronization of the clock of the receiving circuitry is achieved bydetecting the synchronization marker S". Subsequent processing of thestored frames with the BCH error correction code being reprocessed afterresynchronization of the receiving circuitry may yield additional validdata as illustrated, for example, in FIG. 23 as discussed above.Processing proceeds to decision point 862 where a determination is madeif errors are present in the data bits of the fetched frame. If theanswer is "no" at decision point 862, processing proceeds to point 864where the data bits of all previous frames are fetched beginning withthe frames where at least one erroneous uncorrectable bit was firstdetected and the position of erroneous uncorrectable bits within theframe is checked in the manner described above with respect to FIGS.23-25 using pattern recognition in order to attempt to reconstruct validdata such as the example of FIG. 23 where each of the frames within theDATA FRAME GROUP are reconstructed as having valid data as a consequenceof the erroneous uncorrectable bits in a series of zeros or ones beingtotally contained within the BCH error correction code bit field.Processing proceeds to decision point 866 where a determination is madewhether the error correction code bits contain any erroneous bits. Ifthe answer is "no" at decision point 866, processing proceeds todecision point 868 where a determination is made, are any erroneousuncorrectable bits within the data unit bits of the frame? If the answeris "yes" at decision point 868, processing proceeds to point 870 whereerror markers are placed for each of the faded data units of the frameas a consequence of there being at least one erroneous uncorrectable bitwithin the data bits of the frame which is indicative of invalid data.If the decision is "yes" at decision point 866, processing proceeds topoint 872 where all of the bits of the data units are stored as validdata. Similarly, if the answer is "no" at decision point 868, processingproceeds to point 872. From point 872 processing proceeds to point 874where the data unit counter is incremented by the number of data unitsin a frame which, in the present example, is equal to three. Processingproceeds from point 874 back to decision point 814 as described above.If the answer is "yes" at decision point 862, processing proceeds topoint 876 where a group of bits equal to the number of bits in the nextDATA FRAME GROUP are fetched from the digital buffer followed by thedigital signal processor processing the bits of the FRAME GROUP with theBCH error code polynomial followed by storing in the digital signalprocessor temporary buffer the result of the processing including savingof the BCH error code. The processing proceeds to decision point 878where a determination is made if there are any erroneous uncorrectablebits in the next FRAME GROUP bits which were fetched at point 876. Ifthe answer is "no" at decision point 878, processing proceeds to point864 as previously described as a result of the determination at decisionpoint 876 that there are no errors present in any of the bits which isindicative of synchronization not being lost. As a result, at point 864as previously described, the previous frames which have been identifiedas containing any erroneous uncorrectable bits are processed within theframes in accordance with the discussion at FIGS. 23-25 above to performreconstruction to recover previously unrecoverable data by looking forframes without errors exceeding the bit error correction of the errorcorrection code or when the bit error correction capacity is exceededbit patterns indicative of the uncorrectable bit errors being presenttotally within the bit field of the error correction code are found. Ifthe answer is "yes" at decision point 878, the fetched FRAME GROUP ofbits which contains one or more erroneous uncorrectable bits is shiftedby the digital signal processor to locate a synchronization marker S" asdescribed above to achieve resynchronization. Processing proceeds todecision point 882 where a determination is made if the shifting of thebits to look for the synchronization marker S" at point 882 has beensuccessful in determining the presence of a synchronization marker S".If the answer is "yes" at decision point 882, processing proceeds topoint 884 where the resynchronization of the clock of the receivingcircuitry is performed in accordance with known techniques by locatingthe synchronization marker S" with known techniques. Processing proceedsfrom point 884 to point 864 as described above. If the answer is "no" atdecision point 882, processing proceeds to point 886 where the nextFRAME GROUP bits which are equal to 180 bits when the format inaccordance with FIGS. 5A-5C is used are fetched and the FRAME GROUP bitsare shifted by the digital signal processor to look for thesynchronization marker S". Processing proceeds to decision point 888which is analogous to decision point 882. If the answer is "yes" atdecision point 888 that a synchronization marker S" is present in thefetched next DATA FRAME GROUP, processing proceeds to point 884 wherethe resynchronization of the clock occurs as described above. If theanswer is "no" at decision point 888, processing proceeds through aseries of processings analogous to point 886 and decision point 888 tocontinue to look for a synchronization marker S". The number of repeatedfetching steps of the next DATA FRAME GROUP bits and shifting of theDATA FRAME GROUP bits to look for the synchronization marker S" followedby the determination of whether a synchronization marker S" is presentis chosen to consume a time of processing at least equal to the longestduration fade which is statistically likely to occur which studies haveshown is somewhere between three and five hundred milliseconds. If therepeating of the fetching of the next DATA FRAME GROUP bits and shiftingDATA FRAME GROUP bits to look for a synchronization marker S" followedby the determination is a synchronization marker S" present sequencesthrough a time interval of 300 to 500 milliseconds, it is unlikely thata fade is present because fades of this duration are statisticallyimprobable and the transmission is statistically likely to be over.Thereafter, processing proceeds to point 890 where the digital signalprocessor buffer is cleared which is indicative of the transmission ofthe frames being completed. Thereafter, processing proceeds to point 892where data unit error markers are stored in each of the frames whichhave been detected to have at least one erroneous uncorrectable databit. Thereafter processing proceeds to point 814 as described above.

If the frame format of FIG. 5D is used, the processing of FIGS. 26A-Cwould be simplified to eliminate processing of synchronization markersS" and the FRAME GROUP # because of the shortening of the total numberof frames being contained in one ID FRAME GROUP. The resultantprocessing would involve the steps associated with reconstruction asdiscussed above.

FIG. 27 illustrates an example of the processing which occurs when aloss of synchronization is detected followed by the subsequent detectionof the synchronization marker S" which resynchronizes receivingcircuitry of the clock. As illustrated, a plurality of frames are firstdetected and processed with the error correction code to identifyerroneous uncorrectable bits, which are identified for illustrationpurposes by the letter "E" as used above in FIGS. 23-25. In accordancewith the processing described above in FIGS. 26A-26C, after one or moresuccessive frames are processed with the error correction code todetermine the presence of at least one erroneous uncorrectable bit,which exceeds the bit error correction capacity of the error correctioncode as discussed above, the digital signal processor proceeds inaccordance with the clock timing of the receiving circuitry requiringresynchronization. The detected bits of the frames beginning from FRAMEGROUP #3 where the presence of the loss of synchronization is detectedby the aforementioned detection of one or more frames having at leastone erroneous uncorrectable bit which are stored in the memoryassociated with the digital signal processor are searched by shiftingthe stored bits in memory to look for the synchronization marker S". Asillustrated, bits corresponding to where DATA FRAME GROUP #4 should befound contain successive erroneous uncorrectable bits followed by atotal loss of detection of valid data, followed by a detection of asynchronization marker S" in DATA FRAME GROUP #12. As a result, thedigital signal processor is able resynchronize its clock at FRAME GROUP#12 and determine that a total of eight DATA FRAME GROUPS have been lostduring the fade of the wireless transmission below the detectioncapability of the receiving circuitry which requires reconstruction totry to identify and recover valid data as described above. Afterresynchronization is accomplished by detection of the synchronizationmarker S", groups of forty five bits, which are the number of bitscontained in a frame of the example above, will be processed with theresynchronized proper clock timing which permits both forward orbackward processing by the digital signal processor of each of theframes of data which are located beginning with the DATA FRAME GROUP inwhich synchronization was first detected as being lost and to andthrough the subsequent DATA FRAME GROUP in which the synchronizationmarker S" was detected reestablishing resynchronization. As a result, itmay be possible to recover and reconstruct many of the frames of datawhich otherwise would have been lost because of the loss ofsynchronization which was not correctable with the prior art's solereliance on error correction code. The recovery and reconstructionprocessing of the frames of data is in accordance with that describedabove with respect to frames 23-25 including storing as valid data unitsall frames which, when processed after resynchronization, do not containany erroneous uncorrectable bits while discarding the bits of the errorcorrection code and those frames which contain erroneous uncorrectablebits totally in the bit field of the error correction field as discussedabove while discarding the bits of the error correction code. All frameswhich contain erroneous uncorrectable bits which are not totally in thebit field of the error correction code are stored as erroneous dataunits with the bits of the error correction code being discarded.

Furthermore, subsequent processing of frames after the detection of thesynchronization marker S" in DATA FRAME GROUP #12 will be in accordancewith the previously described procedure in which synchronization ispresent because of the resynchronization of the clock of the receivingcircuitry. Each frame transmitted in time after the subsequentlydetected synchronization marker in DATA FRAME GROUP #12 is processed inaccordance with normal procedures in which synchronization is present.Each frame is tested to determine if any erroneous uncorrectable bitsare present, if no erroneous uncorrectable bits are present in a framethe data units of the frames are stored as valid and the bits of theerror correction code are discarded, if erroneous uncorrectable bits arepresent and determined to be present only in the field of the BCH errorbits within the frame by using the aforementioned pattern recognition ofthe frame bits, all of the data bits are stored as valid and the bits ofthe error correction code are discarded, and if erroneous uncorrectablebits are not totally contained in the bit field of the error correctioncode, the data units are stored as invalid data by storing errorcharacters and the bits of the error code filed are discarded.

Thus, it is seen that the present invention provides four methodologiesfor improving reception reliability which are (1) reconstructionprocessing of frames containing erroneous uncorrectable bits presenttotally within the BCH error correction code bits of the frame, (2)resynchronization of the clock of the receiving circuitry, (3)reconstruction processing of the frames located beginning where the lossof synchronism is detected in one or more frames containing at least oneerroneous uncorrectable data bit to the frames in the DATA FRAME GROUPwhere resynchronization is reestablished by detection of thesynchronization marker S" and (4) normal processing of the framestransmitted after the detected synchronization marker S" includingreconstruction of those frames determined to have at least one erroneousuncorrectable error and/or further resynchronization. Theresynchronization of the clock provides correct timing for processingthe groups of bits in a frame to again determine if the bits contain anyerroneous uncorrectable data bits, if any erroneous uncorrectable databits are present, are they totally present within the bits of the fieldof the BCH error correction code field within the frame and when thebits are totally with the bits of the field of the BCH error code thedata bits are stored as reconstructed valid data bits while discardingthe bits of the error correction code.

The at least one digital signal processor of the receiving circuitryfunctions to detect bits modulated on the subcarrier within thetransmitted at least one identification frame within the ID Frame Groupof FIG. 5A and the plurality of DATA FRAME GROUPS of FIG. 5B or the IDFRAME GROUP of FIG. 5D and causes storage of the detected bits withinthe at least one ID FRAME GROUP and the plurality of DATA FRAME GROUPSin the memory associated with the at least one processor. Thereafter,the at least one digital signal processor processes the stored bits ofthe at least one frame of at least one of the plurality of DATA FRAMEGROUPS with the error correction code therein to determine when thestored bits of the at least one frame contain at least one uncorrectableerroneous bit, as illustrated in FIGS. 23-25 and 27 discussed above,which cannot be corrected with the error correction code therein. The atleast one digital signal processor causes searching of the stored bitsin the memory associated with the at least one digital signal processorwhich are transmitted after the stored bits of the at least oneprocessed frame containing the at least one uncorrectable erroneous bitto detect a synchronization marker S" as described above in conjunctionwith FIG. 27 to resynchronize the clock of the receiving circuitry wheredetermined to be necessary. Preferably, the at least one digital signalprocessor processes the stored bits of a plurality of frames of at leastone of the plurality of DATA FRAME GROUPS with the error correction codetherein as described above in conjunction with steps 850 and 876 todetermine when the stored bits of the plurality of frames each containat least one uncorrectable erroneous bit which cannot be corrected withthe error correction code therein prior to searching the stored detectedbits transmitted after the stored bits of the plurality of frames eachcontaining the at least one uncorrectable erroneous bit to detect asynchronization marker S". The bits of the detected synchronizationmarker S" which are detected at decision points 882 and 888, asdescribed above, resynchronize the receiving circuitry clock permittingreconstruction processing of the bits of frames in at least one DATAFRAME GROUP which contain a FRAME GROUP # address identifying a DATAFRAME GROUP transmitted before, within or after the data frame groupcontaining the detected synchronization marker S" as indicated by thestep 884 in FIG. 26C resynchronizing the clock and further inconjunction with point 864, decision point 866, point 868, point 870 andpoint 872 as described above in conjunction with FIG. 26B. As has beendescribed above, the resynchronization of the clock at point 884 isperformed by using conventional bit shifting procedures in memory orregisters to locate the synchronization marker S" within the storedinformation transmitted after the detection of loss of synchronizationby finding at least one frame having at least one erroneousuncorrectable bit.

Once resynchronization is established, which involves the changing ofthe clock timing of the receiving circuitry by one or more clock cycleswhich correspond to the number of bits which have been lost or gainedduring a fade by detecting the synchronization marker S", reconstructionof a number of frames which is determined from the DATA FRAME GROUP #associated with the DATA FRAME GROUP which contains the detectedsynchronization marker S" is performed. The digital signal processorcalculates the number of frames requiring reconstruction beginning withthe frames where the loss of synchronization was detected by at leastone frame having at least one erroneous uncorrectable bit to the framesin the DATA FRAME GROUP containing the detected synchronization markerS" by using the difference in the FRAME GROUP #s of the DATA FRAMEGROUPS containing the at least one frame containing at least oneerroneous uncorrectable bit and the synchronization marker as indicatedby step 884 in FIG. 26A. Thereafter, groups of bits equal to the numberof bits in a frame, which are forty five bits as described above in theexample of the protocol of the present invention in FIGS. 5A and B andFIG. 5D, are sequentially fetched and checked by processing the errorcode therein to determine if any erroneous uncorrectable bits arepresent. This process may be performed either in a forward or backwardaddress direction from the at least one frame containing at least oneerroneous uncorrectable bit to the detected synchronization marker S"which corresponds to the frame containing data unit four of FRAME GROUP#13 and the frame containing data unit one of FRAME GROUP #12 in FIG.27. Thereafter, with resynchronization being established, the individualframes transmitted after FRAME GROUP #12 are processed with the errorcorrection code and where necessary, the pattern recognition techniquesof the digital signal processor are used to determine where theerroneous uncorrectable bits are present within each frame in the manneras discussed above with FIGS. 23-25 including resynchronization wheresynchronization is again lost by searching for another subsequentlytransmitted synchronization marker.

The protocol of the invention is applicable for all facets of one-wayand two-way telecommunications. It, in essence, permits wireless serialtransmission of all forms of digitalized information to move forward tosend extremely high information transmission rates to a receiver ortwo-way transceiver with an improved reliability when compared to theprior art. This increases the reliability of one-way radio messaging tomake it suitable for E-mail and information services as well as permitsa much greater number of subscribers to exist on a radio paging channel.The protocol of the present invention with a 2400 Hz. subcarrier allowsa ten to twenty times increase of data throughput in receiving circuitryutilizing the same radio transmitter infrastructure used, for example,with the POCSAG protocol. More importantly, this additional air timeaddresses the E-mail and information services with a higher degree ofreliability achievable with prior art one-way protocols withoutnecessitating the use for two-way radio channels. The protocol alsopermits two-way data services to experience dramatic gains in air timeefficiency and a corresponding increase of subscribers per channel byeliminating some requests for retransmission of information caused by atleast a part of a message being lost.

Having a higher message reception probability and a higher throughputcapacity has a net effect of saving a data service company many millionsof dollars by eliminating the necessity for additional radio spectrum.Regardless of the transmitting bandwidth or the data rates, theinvention will produce a significant increase in system efficiency. Anadded advantage is that it can utilize current radio frequencies in the150, 220, 450, 800 and 900 MHz transmitting bands and higher frequencybands to accommodate information and E-mail services. This is far lessexpensive than implementing such services at the proposed 1.2 and 2.4GHz radio bands which will be auctioned in the future by the FederalCommunications Commission. The E-mail and information servicesindustries could be immediately addressed with the currentinfrastructure to accommodate wireless services.

While the invention has been described in terms of its preferredembodiments and methods of operation, it should be understood thatnumerous modifications may be made thereto without departing form thespirit and scope of the invention. For example, it should be understoodthat the invention is not limited with regard to the type of informationwhich may be serially transmitted. Any type of data may be transmittedin practicing the invention which may be digitized and used to controlthe analog modulation of information as illustrated in FIG. 6A or thedigital modulation of information as illustrated in FIG. 6B. Theinvention is not limited to any fixed architecture in the transmittingand receiving circuitry including the choice of the number and type ofprocessors which are used. The number of memories and/or the allocationof how the at least one processor of the receiving circuitry stores bitsof processed frames in memory may be varied in practicing the invention.Either a single or multiple memories may be used to store the processedbits of the frames which are processed by the at least one processor.Finally, it should be understood that the choice of and number ofintegrated circuits for implementing the transmitting circuitry andreceiving circuitry, as illustrated in FIGS. 12 and 13, may be varied inpracticing the invention depending upon the application of the presentinvention including cost and functional constraints of the application.It should be understood that the present invention may be modified fromthe above description thereof without departing from its spirit andscope. It is intended that all such modifications fall within the scopeof the appended claims.

I claim:
 1. A process for transmitting a plurality of frames ofinformation with a radio frequency carrier comprising:modulating asubcarrier with at least one identification frame group which identifiesreceiving circuitry to receive the information followed at least onedata group, each identification frame group at least one framecontaining bits identifying the circuitry to receive the radio frequencycarrier, a plurality of bits of error correction code in each frame, andsynchronization information for originally synchronizing a clock of thereceiving circuitry and a synchronization marker comprised of aplurality of bits for resynchronizing the clock of the receivingcircuitry, and each data frame group having at least one frame eachincluding a plurality of bits of error correction code and a pluralityof bits of data, and another synchronization marker comprised of aplurality of bits for resynchronizing the clock of the receivingcircuitry during the transmission of the plurality of frames ofinformation when a loss of synchronization of the clock is detected bythe receiving circuitry during the transmission of the plurality offrames; modulating the radio frequency carrier with the modulatedsubcarrier; and transmitting the modulated carrier.
 2. A process inaccordance with claim 1 wherein:each frame group contains a frame groupaddress comprised of a plurality of bits which identify a unique addressof the frame group within the plurality of frames of transmittedinformation.
 3. A process in accordance with claim 1 wherein:cycles ofthe subcarrier are modulated with pulse width modulation with a width ofparts of the subcarrier being modulated with at least one bit of theframes of the information.
 4. A process in accordance with claim 1wherein:cycles of the subcarrier are modulated with bits encoding theplurality of frames of information with each cycle of the subcarrierbeing modulated by the bits at a plurality of separated angularpositions.
 5. A process in accordance with claim 2 wherein:cycles of thesubcarrier are modulated with pulse width modulation with a width ofparts of the subcarrier being modulated with at least one bit of theframes of the information.
 6. A process in accordance with claim 2wherein:cycles of the subcarrier are modulated with bits encoding theplurality of frames of information with each cycle of the subcarrierbeing modulated by the bits at a plurality of separated angularpositions.
 7. A process in accordance with claim 1 wherein:thesynchronization information also contains bits identifying the receivingcircuitry.
 8. A process in accordance with claim 2 wherein:thesynchronization information also contains bits identifying the receivingcircuitry.
 9. A process in accordance with claim 3 wherein:thesynchronization information also contains bits identifying the receivingcircuitry.
 10. A process in accordance with claim 4 wherein:thesynchronization information also contains bits identifying the receivingcircuitry.
 11. A process in accordance with claim 5 wherein:thesynchronization information also contains bits identifying the receivingcircuitry.
 12. A process in accordance with claim 6 wherein:thesynchronization information also contains bits identifying the receivingcircuitry.
 13. A process in accordance with claim 1 wherein:theidentification frame group also contains a command field containing atleast one bit for commanding a function to be performed by the receivingcircuitry.
 14. A process in accordance with claim 2 wherein:theidentification frame group also contains a command field containing atleast one bit for commanding a function to be performed by the receivingcircuitry.
 15. A process in accordance with claim 3 wherein:theidentification frame group also contains a command field containing atleast one bit for commanding a function to be performed by the receivingcircuitry.
 16. A process in accordance with claim 4 wherein:theidentification frame group also contains a command field containing atleast one bit for commanding a function to be performed by the receivingcircuitry.
 17. A process in accordance with claim 5 wherein:theidentification frame group also contains a command field containing atleast one bit for commanding a function to be performed by the receivingcircuitry.
 18. A process in accordance with claim 6 wherein:theidentification frame group also contains a command field containing atleast one bit for commanding a function to be performed by the receivingcircuitry.
 19. A process in accordance with claim 7 wherein:theidentification frame group also contains a command field containing atleast one bit for commanding a function to be performed by the receivingcircuitry.
 20. A process in accordance with claim 8 wherein:theidentification frame group also contains a command field containing atleast one bit for commanding a function to be performed by the receivingcircuitry.
 21. A process in accordance with claim 9 wherein:theidentification frame group also contains a command field containing atleast one bit for commanding a function to be performed by the receivingcircuitry.
 22. A process in accordance with claim 10 wherein:theidentification frame group also contains a command field containing atleast one bit for commanding a function to be performed by the receivingcircuitry.
 23. A process in accordance with claim 11 wherein:theidentification frame group also contains a command field containing atleast one bit for commanding a function to be performed by the receivingcircuitry.
 24. A process in accordance with claim 12 wherein:theidentification frame group also contains a command field containing atleast one bit for commanding a function to be performed by the receivingcircuitry.
 25. Transmitting circuitry for transmitting a plurality offrames of information with a radio frequency carrier comprising:anencoder for modulating a subcarrier with at least one identificationframe group which identifies receiving circuitry to receive theinformation followed by at least one data frame group with eachidentification frame group comprising at least one frame containing bitsidentifying the receiving circuitry to receive the radio frequencycarrier, a plurality of bits of error correction code in each frame,synchronization information for originally synchronizing a clock of thereceiving circuitry, and a synchronization marker comprised of aplurality of bits for resynchronizing the clock of the receivingcircuitry with each data frame group comprising at least one frame eachincluding a plurality of bits of error correction code and a pluralityof bits of data, and another synchronization marker comprised of aplurality of bits for resynchronizing the clock of the receivingcircuitry during the transmission of the plurality of frames ofinformation when a loss of synchronization of the clock is detected bythe receiving circuitry during the transmission of the plurality offrames; a modulator, coupled to the encoder, for modulating the radiofrequency carrier with the subcarrier; and a transmitter, coupled to themodulator, for transmitting the modulated carrier.
 26. Transmittingcircuitry in accordance with claim 25 wherein:each frame group containsa frame group address comprised of a plurality of bits which identify aunique address of the frame group within the plurality of frames oftransmitted information.
 27. Transmitting circuitry in accordance withclaim 25 wherein:cycles of the subcarrier are modulated with pulse widthmodulation with a width of parts of the subcarrier being modulated withat least one bit of the frames of the information.
 28. Transmittingcircuitry in accordance with claim 25 wherein:cycles of the subcarrierare modulated by the encoder with bits encoding the plurality of framesof information with each cycle of the subcarrier being modulated by thebits at a plurality of separated angular positions.
 29. Transmittingcircuitry in accordance with claim 26 wherein:cycles of the subcarrierare modulated with pulse width modulation with a width of parts of thesubcarrier being modulated with at least one bit of the frames of theinformation.
 30. Transmitting circuitry in accordance with claim 26wherein:cycles of the subcarrier are modulated by the encoder with bitsencoding the plurality of frames of information with each cycle of thesubcarrier being modulated by the bits at a plurality of separatedangular positions.
 31. Transmitting circuitry in accordance with claim25 wherein:the synchronization information also includes bitsidentifying the receiving circuitry.
 32. Transmitting circuitry inaccordance with claim 26 wherein:the synchronization information alsoincludes bits identifying the receiving circuitry.
 33. Transmittingcircuitry in accordance with claim 27 wherein:the synchronizationinformation also includes bits identifying the receiving circuitry. 34.Transmitting circuitry in accordance with claim 28 wherein:thesynchronization information also includes bits identifying the receivingcircuitry.
 35. Transmitting circuitry in accordance with claim 29wherein:the synchronization information also includes bits identifyingthe receiving circuitry.
 36. Transmitting circuitry in accordance withclaim 30 wherein:the synchronization information also includes bitsidentifying the receiving circuitry.
 37. Transmitting circuitry inaccordance with claim 25 wherein:the identification frame group alsocontains a command field containing at least one bit for commanding afunction to be performed by the receiving circuitry.
 38. Transmittingcircuitry in accordance with claim 26 wherein:the identification framegroup also contains a command field containing at least one bit forcommanding a function to be performed by the receiving circuitry. 39.Transmitting circuitry in accordance with claim 27 wherein:theidentification frame group also contains a command field containing atleast one bit for commanding a function to be performed by the receivingcircuitry.
 40. Transmitting circuitry in accordance with claim 28wherein:the identification frame group also contains a command fieldcontaining at least one bit for commanding a function to be performed bythe receiving circuitry.
 41. Transmitting circuitry in accordance withclaim 29 wherein:the identification frame group also contains a commandfield containing at least one bit for commanding a function to beperformed by the receiving circuitry.
 42. Transmitting circuitry inaccordance with claim 30 wherein:the identification frame group alsocontains a command field containing at least one bit for commanding afunction to be performed by the receiving circuitry.
 43. Transmittingcircuitry in accordance with claim 31 wherein:the identification framegroup also contains a command field containing at least one bit forcommanding a function to be performed by the receiving circuitry. 44.Transmitting circuitry in accordance with claim 32 wherein:theidentification frame group also contains a command field containing atleast one bit for commanding a function to be performed by the receivingcircuitry.
 45. Transmitting circuitry in accordance with claim 33wherein:the identification frame group also contains a command fieldcontaining at least one bit for commanding a function to be performed bythe receiving circuitry.
 46. Transmitting circuitry in accordance withclaim 34 wherein:the identification frame group also contains a commandfield containing at least one bit for commanding a function to beperformed by the receiving circuitry.
 47. Transmitting circuitry inaccordance with claim 35 wherein:the identification frame group alsocontains a command field containing at least one bit for commanding afunction to be performed by the receiving circuitry.
 48. Transmittingcircuitry in accordance with claim 36 wherein:the identification framegroup also contains a command field containing at least one bit forcommanding a function to be performed by the receiving circuitry.
 49. Aprocess for transmitting a plurality of frames of information with aradio frequency carrier comprising:modulating a subcarrier withsynchronization information for originally synchronizing a clock ofreceiving circuitry to receive the plurality of frames of theinformation, at least one frame group comprising at least one frame witheach frame comprising a plurality of bits of error correction code and aplurality of other bits and a synchronization marker comprised of aplurality of bits for resynchronizing the clock of the receivingcircuitry after initial synchronization of the clock by reception of thesynchronization information during the transmission of the plurality offrames of information when a loss of synchronization of the clock isdetected by the receiving circuitry during the transmission of theplurality of frames; modulating a radio frequency carrier with themodulated subcarrier; and transmitting the modulated carrier.
 50. Aprocess in accordance with claim 49 wherein:each frame group contains aframe group address comprised of a plurality of bits which identify aunique address of the frame group within the plurality of frames oftransmitted information.
 51. A process in accordance with claim 49wherein:cycles of the subcarrier are modulated with pulse widthmodulation with a width of parts of the subcarrier being modulated withat least one bit of the frames of the information.
 52. A process inaccordance with claim 49 wherein:cycles of the subcarrier are modulatedwith bits encoding the plurality of frames of information with eachcycle of the subcarrier being modulated by the bits at a plurality ofseparated angular positions.
 53. A process in accordance with claim 50wherein:cycles of the subcarrier are modulated with pulse widthmodulation with a width of parts of the subcarrier being modulated withat least one bit of the frames of the information.
 54. A process inaccordance with claim 53 wherein:cycles of the subcarrier are modulatedwith bits encoding the plurality of frames of information with eachcycle of the subcarrier being modulated by the bits at a plurality ofseparated angular positions.
 55. A process in accordance with claim 49wherein:the at least one frame group also contains a command fieldcontaining at least one bit for commanding a function to be performed bythe receiving circuitry.
 56. A process in accordance with claim 50wherein:the at least one frame group also contains a command fieldcontaining at least one bit for commanding a function to be performed bythe receiving circuitry.
 57. A process in accordance with claim 51wherein:the at least one frame group also contains a command fieldcontaining at least one bit for commanding a function to be performed bythe receiving circuitry.
 58. A process in accordance with claim 52wherein:the at least one frame group also contains a command fieldcontaining at least one bit for commanding a function to be performed bythe receiving circuitry.
 59. A process in accordance with claim 53wherein:the at least one frame group also contains a command fieldcontaining at least one bit for commanding a function to be performed bythe receiving circuitry.
 60. A process in accordance with claim 54wherein:the at least one frame group also contains a command fieldcontaining at least one bit for commanding a function to be performed bythe receiving circuitry.
 61. Transmitting circuitry for transmitting aplurality of frames of information with a radio frequency carriercomprising:an encoder for modulating a subcarrier with synchronizationinformation for originally synchronizing a clock of receiving circuitryto receive the plurality of frames of the information, at least oneframe group comprising at least one frame with each frame comprising aplurality of bits of error correction code and a plurality of otherbits, and a synchronization marker comprised of a plurality of bits forresynchronizing the clock of the receiving circuitry after initialsynchronization of the clock by reception of the synchronizationinformation during the transmission of the plurality of frames ofinformation when a loss of synchronization of the clock is detected bythe receiving circuitry during the transmission of the plurality offrames; a modulator, coupled to the encoder, for modulating a radiofrequency carrier with the subcarrier; and a transmitter, coupled to themodulator, for transmitting the modulated carrier.
 62. Transmittingcircuitry in accordance with claim 61 further comprising:each framegroup containing a frame group address comprised of a plurality of bitswhich identify a unique address of the frame group within the pluralityof frames of wirelessly transmitted information.
 63. Transmittingcircuitry in accordance with claim 61 wherein:cycles of the subcarrierare modulated with pulse width modulation with a width of parts of thesubcarrier being modulated with at least one bit of the frames of theinformation.
 64. Transmitting circuitry in accordance with claim 61wherein:cycles of the subcarrier are modulated by the encoder with bitsencoding the plurality of frames of information with each cycle of thesubcarrier being modulated by the bits at a plurality of separatedangular positions.
 65. Transmitting circuitry in accordance with claim62 wherein:cycles of the subcarrier are modulated with pulse widthmodulation with a width of parts of the subcarrier being modulated withat least one bit of the frames of the information.
 66. Transmittingcircuitry in accordance with claim 62 wherein:cycles of the subcarrierare modulated by the encoder with bits encoding the plurality of framesof information with each cycle of the subcarrier being modulated by thebits at a plurality of separated angular positions.
 67. Transmittingcircuitry in accordance with claim 61 wherein:the at least one framegroup also contains a command field containing at least one bit forcommanding a function to be performed by the receiving circuitry. 68.Transmitting circuitry in accordance with claim 62 wherein:the at leastone frame group also contains a command field containing at least onebit for commanding a function to be performed by the receivingcircuitry.
 69. Transmitting circuitry in accordance with claim 63wherein:the at least one frame group also contains a command fieldcontaining at least one bit for commanding a function to be performed bythe receiving circuitry.
 70. Transmitting circuitry in accordance withclaim 64 wherein:the at least one frame group also contains a commandfield containing at least one bit for commanding a function to beperformed by the receiving circuitry.
 71. Transmitting circuitry inaccordance with claim 65 wherein:the at least one frame group alsocontains a command field containing at least one bit for commanding afunction to be performed by the receiving circuitry.
 72. Transmittingcircuitry in accordance with claim 65 wherein:the identification framegroup also contains a command field containing at least one bit forcommanding a function to be performed by the receiving circuitry. 73.Transmitting circuitry in accordance with claim 66 wherein:theidentification frame group also contains a command field containing atleast one bit for commanding a function to be performed by the receivingcircuitry.